Act 1 mainly consists of romancing three of the four girls: Sayori, Yuri, and Natsuki. It is the only act without any glitches or jump-scares as Monika has not yet begun to break the game or alter the personalities of the other girls (other than Sayori and the scene where she hangs herself as the manipulation by Monika begins). Throughout the act, the game appears to be a stereotypical romance visual novel.
In this act, the protagonist writes poems for Sayori, Yuri, or Natsuki. The protagonist talks to each of them and spends time with his/her chosen lover; Sayori usually likes the protagonist's poems regardless of whom the protagonist wrote them for (because most of the poem game words give her extra points, making it very hard to make Sayori dislike a poem), but comments later that she knows the protagonist wrote them for Natsuki or Yuri (defaulting on Yuri in case the poems were all directed towards her). While she tries to hide her sorrow, it is apparent that losing the protagonist's attention bothers Sayori.
Sayori will be the only person who confesses to the protagonist in Act 1. While rejecting her confession results in heartbreak, accepting her confession does not alter the path of the game, save for a few lines of dialogue and a CG. Although on the surface the game does not appear to have been altered yet, Sayori's personality has seen a fundamental change over the course of Act 1. She turns from a happy, bubbly personality to a more melancholy, bittersweet one (and from depressed to all-out suicidal in the span of just a few days). Monika's tampering with her depression is heavily implied (and later explicitly stated) to have played a part. Act 1 will end when the protagonist sees Sayori's body hanging in her room and the player is sent back to the title screen.
If the protagonist chooses to write for Natsuki, the second day will have them find her searching for her manga in the classroom closet. The protagonist will then proceed to spend the club time with her, reading the manga, Parfait Girls, which Natsuki particularly likes. The player will receive a CG of them reading the manga.
Once the time to share poems arrives, Monika, Sayori, and Yuri comment on the likeness to Natsuki's writing style, whereas Natsuki is flustered and dismisses the protagonist's poem as merely "okay," showing traits typical of the tsundere type to which she is likened.
If the protagonist chooses to write for Yuri, the second day will entail reading a book which she had bought for them (although she denies doing this), which shows a CG of reading beside each other from the same book. The protagonist makes comments on how the book's protagonist reminds him of Yuri, to which Yuri becomes extremely embarrassed.
When sharing the protagonist's poem with Yuri, she is taken aback but provides constructive feedback for the protagonist to consider and use to improve their writing style.
If the protagonist chooses to write for Sayori, in the second day the main character to fall asleep, to then be woken up by Sayori. The protagonist will comment that Sayori takes better care of him than she does for herself and points out some flaws in Sayori's appearance, which leads to a CG of the main character buttoning up Sayori's blazer.
When sharing the protagonist's poem with Sayori, she states that she likes it a lot and when the protagonist reads her poem, he mocks her for writing hers on the day itself.
After sharing the protagonist's poem with all four girls, the protagonist notices Yuri and Natsuki in the process of sharing theirs. Natsuki remarks that Yuri's poem is "fancy," to which Yuri responds by saying hers is "cute," offending Natsuki. The two then argue about their writing styles, eventually leading to Natsuki accusing Yuri of trying to impress the protagonist. Insulted, Yuri tells Natsuki that she is just jealous, but Natsuki only responds by telling Yuri to stop being full of herself. The argument eventually evolves into a full-fledged fight, with Yuri mocking Natsuki for being cute and Natsuki accusing Yuri of padding her bra. The protagonist then has to decide how to respond. Whoever he picks also gets 5 extra points for the next poem game.
If the protagonist agrees with Natsuki, Natsuki becomes proud and happily accepts the protagonist's opinion, only for the protagonist to chide her when Yuri becomes upset. Natsuki then reluctantly apologizes to Yuri.
If the protagonist agrees with Yuri, he tells her that Natsuki's writing style should not be ridiculed and Yuri apologizes. The protagonist then tells Natsuki that she took it way too far, only for Natsuki to refute, saying that Yuri started the argument. Monika steps in, reminding Natsuki that Yuri already apologized, prompting her to do the same, but Natsuki, clearly angry with the lack of support for her, leaves the room.
If the protagonist instead asks Sayori for help, Sayori will go on to praise both girls for their writing styles, but also accidentally causes more awkwardness, causing Yuri and Natsuki to both become embarrassed. The protagonist then praises Sayori in front of Monika.
On day three, Monika is found to have moved all of Natsuki's manga up to the top shelf, and Natsuki is forced to find a way to reach them. This awards the player with a CG as the protagonist holds onto the chair while Natsuki grabs the box of manga, in a position where the protagonist can almost see up her skirt. Once she has the box, she asks the protagonist to take it, but she changes her mind as she looks down and thinks that the protagonist is perving her out. Her anger in this situation causes her to fall, and she lands on top of the protagonist, accidentally causing him to crease a page in one of the manga. She cries when she fails to remove the crease, and the protagonist decides to help her clear up her mess and cheer her up, causing her to tell him that he is nice to her, which is not a usual thing for her to say, confusing the protagonist.
When sharing poems, Natsuki is even more flustered than on day two, struggling to admit that she likes his poem.
On the third day, Yuri and the protagonist continue where they left off in the book from the second day. Yuri requests to sit against the wall on the floor, rather than at the desks, due to her frequent back pain. The protagonist suggests this is due to her bad reading posture, which Yuri goes along with in embarrassment. Yuri goes to get tea with the protagonist, but Monika interjects, stating it is a one-person thing, to which Yuri coldly responds that it is none of her business. Once outside, Yuri immediately regrets saying that and the protagonist reassures her. Yuri notes that the protagonist is being very nice to her and states that she likes being friends with him. When they get back, Yuri expresses how she cannot hold chocolate while holding her book, prompting the protagonist to feed her them, earning the player a CG in the process. When the protagonist does feed her chocolate, Yuri gets embarrassed, but Monika interrupts them before anything else can happen.
When sharing poems, Yuri is even more impressed with the protagonist's poems, noting all the different techniques the protagonist used and can use.
On day three, Sayori asks the protagonist to help her find supplies for the posters that she and Monika plan to make for the festival. She explains what is planned for the event as they search for an empty classroom, and demonstrates a poetry performance. When they find a room, Sayori immediately finds a box of crayons, then drops one. While she bends over to pick it up, she smacks her head on the shelf. The protagonist suggests that he find something cold to put on her head, which rewards the player with a CG of Sayori holding a bottle of apple juice to her head. Sayori then comments on how she misses the times she and the protagonist grew up together.
When sharing poems, Sayori remarks that she is once again impressed and that she loves reading them. The protagonist then admits that he writes his poems better when he keeps thinking of Sayori, which causes her to react in shock.
On day four, when the protagonist enters the clubroom, he notices Sayori staring blankly at her desk. When he asks her what's wrong, Sayori hurriedly dismisses him, causing him to worry. He first asks Monika about her, but Monika says that she does not see anything off with her, but she goes over to talk to her.
When Natsuki approaches the protagonist about reading her manga, he asks her about Sayori as well, causing her to appear jealous and a bit angry. However, after going into more detail, Natsuki calms down and reassures the protagonist that since Sayori is his best friend, if she did have problems, she would bring that up to the protagonist himself.
When sharing poems, Natsuki seems to finally admit that she likes the protagonist's poems, even comparing him to her skills. Natsuki then begs the protagonist to tell her that she is a good writer. When the protagonist asks for her poem, Natsuki becomes very apprehensive and does not show it to him, claiming that it is a bad poem, but she finally gives in and hands it to the protagonist. It is revealed that her poem is actually about the protagonist himself, which is why she was nervous about handing it over. When the protagonist tries to return it, Natsuki declines shyly, saying that she does not want it.
Sayori notes how the protagonist wrote his poem for Natsuki and is clearly upset by something, but before the protagonist can say anything, she leaves the classroom early, claiming she is tired.
After Monika goes over to talk to Sayori, the protagonist notices Yuri staring at him from behind her book. When he asks her about Sayori, Yuri states that she also noticed Sayori's weird behavior and told the protagonist that Sayori could be harboring feelings for him and that Sayori is very lucky to have someone like him care about her.
When sharing poems, Yuri praises the protagonist for his improvement in writing. She then has a heart to heart talk with the protagonist about her love for books and the characters inside them, as well as how she is unable to talk to people due to her low self-esteem. She also tells the protagonist that all these feelings were removed because of the protagonist treating her like everybody else. Unlike Natsuki, she is extremely eager to show her poem, but like Natsuki's, it is a tribute to the protagonist. When the protagonist finishes her poem, she becomes exceptionally flustered and looks away, but the protagonist reassures her that he likes it. Like Natsuki, when the protagonist hands her back her poem, she returns it to him, asking him to keep it.
Sayori again reacts as she did if the protagonist pursues Natsuki.
When sharing poems, Sayori states that it is the protagonist's best poem so far, but the protagonist again asks her what is wrong, only for Sayori to start tearing up and asking the protagonist why he chose not to befriend the other girls. The protagonist claims that he and Sayori have a wavelength, but Sayori only gets sadder, saying how it would be easier on her if the protagonist instead talked to the other girls. When the protagonist gets worried, Sayori quickly dismisses the conversation and heads home.
Normal Route (Beach Poem)
If Yuri or Natsuki do not love or hate the protagonist's poems more than once, they will instead write a normal poem in the subject of beaches.
After sharing poems and Sayori leaving the clubroom, Monika starts her preparations or the festival by handing out duties to each of her members. Monika will be printing pamphlets to promote the club, Sayori will be helping her design them, Natsuki will be baking cupcakes, and Yuri will be creating banners to set the atmosphere for the clubroom, leaving the protagonist to decide on whom to help.
If the protagonist chooses to help Monika, Natsuki and Yuri immediately disagree and tell Monika that her job requires the least amount of work; furthermore, Sayori is already helping her. Monika defends herself, stating that the protagonist chose her, but Natsuki accuses her of scaring him into picking her and Yuri claims that she chose the protagonist for ulterior motives. This causes Monika to defend herself further, rebutting that the two of them also have ulterior motives. Natsuki and Yuri then tell Monika to be more responsible, saying that being alone would lower the standards of their work and that the club's resource should be fairly divided. Monika finally gives in, but even though she agrees with them, she is upset that she is unable to spend any time with the protagonist.
The same thing happens if the protagonist picks Sayori. Natsuki and Yuri again state that Sayori and Monika would be working together. Therefore she would require the least amount of help.
If the protagonist picks Natsuki, she becomes delighted, despite her not wanting any help in the first place. Yuri becomes passive-aggressive, stating that she is used to working alone. Natsuki then notices Yuri once again being upset and starts praising Yuri for her talent in an attempt to cheer her up, which surprises everyone in the club. The protagonist then exchanges phone numbers with her.
If the protagonist picks Yuri, she is taken aback and becomes flustered again. Natsuki claims to not care about the protagonist's decision, but everyone knows that she is miserable about it. Yuri then tries to cheer Natsuki up, praising her talent in baking, which appears to work. The protagonist then exchanges phone numbers with Yuri.
Before the protagonist goes to hang out with either Natsuki or Yuri, he decides to check on Sayori first. Sayori then reveals to the protagonist that she has had bad depression her whole life. The protagonist is taken aback and tries to help Sayori by hugging her and offering to spend the whole day of the festival with her. After that, he suggests skipping his "date" with Yuri or Natsuki, but Sayori tells him not to.
When the protagonist returns home, Natsuki soon arrives, and he lets her into his house. The two get started with baking, but when Natsuki playfully tries to get the protagonist dirty with icing, the player is awarded a CG of him catching Natsuki by both hands. The protagonist then licks the icing off of her finger, causing her to react in shock and embarrassment. After that, when they finish baking, Natsuki laments about how she has no time left to hang out properly with the protagonist. The protagonist agrees and offers to hang out some other time. Natsuki says that she feels the same way and presumably moves in for a kiss, but is interrupted by Sayori.
After the protagonist leaves Sayori's house, he finds Yuri already at his house waiting for him. The two go inside and start preparing the items for the banners. To cut ribbons, Yuri takes out a small pocket knife and goes on to tell the protagonist about her slight obsession with knives. When the protagonist leaves to collect water and returns, he finds Yuri happily unrolling her sleeve. This might be a hint that Yuri cuts herself, but Yuri quickly ends the conversation before the protagonist can continue. Eventually, the protagonist accidentally gets paint on Yuri's face, and the player is rewarded a CG of him wiping her face with a warm towel. When they finish the banners, Yuri states that she wishes to have had more time spent with the protagonist. The protagonist suggests hanging out another time, and a grateful Yuri moves closer to the protagonist, presumably for a kiss, but is interrupted by Sayori.
After Sayori interrupts Yuri and Natsuki, they become flustered and hurry home. Sayori then starts crying, admitting that she is not happy that the protagonist is spending more time with Yuri or Natsuki. Sayori then confesses her true feelings to the protagonist.
If the protagonist accepts her confession, the player is rewarded with a CG of Sayori and the protagonist hugging. The protagonist reassures Sayori that he will be with her to help her through her hardships. Sayori hesitantly accepts this and leaves.
If the protagonist rejects her confession, Sayori becomes heartbroken and despite trying to accept that things are back to the way they were, is unable to control her emotions and screams out loud in agony. Before the protagonist can do anything, she runs off.
On the day of the festival, the protagonist enters the clubroom, and only Monika is inside. Monika reveals that she knows about Sayori's and the protagonist's relationship. When the protagonist reads Sayori's morbidly different poem, he is shocked and horrified and rushes back to her house where he finds her dead, having committed suicide by hanging. The game then abruptly ends, concluding Act 1.