Since there's a few people in the comments who saw the raws and didn't fully understand wh...

Since there's a few people in the comments who saw the raws and didn't fully understand what happened, I'll try to give a full spoiler for what happens (very long so be aware and don't read if you don't want to get spoiled!!!):
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MC considers Seunghyun's (brown haired guy) confession. Chapter 23, Joowon (black haired guy) goes off to take a call and comes back to see MC and Seunghyun laughing and blushing together. He looks kind of jealous/not understanding whats happening between the two of them. Later, Joowon drops Seunghyun off and does it with MC in the car without putting it in and promises later to put it in.

MC goes to Joowon and his brother's house to tutor the brother, and tries to avoid Joowon by telling the brother to go shop with him. But Joowon tells his brother that their parents aren't home right now and he has the chance to play his games (? I think) and the brother ditches MC lol. When they're about to do it, Joowon says that he likes it too (things that feel good). Basically it seems like that he's confessing to MC at first, but later MC realizes he's saying that he likes the sex. MC asks Joowon why he can't just have sex with someone else. Joowon gets a little annoyed and says he's done it with MC 3 times and yet he's telling him to do it with someone else? They do it.

Later MC wakes up in Joowon's arms and snuggles with the sleeping Joowon, reminiscing about their old times together and his crush on him during high school. Then he thinks that Joowon made him think this way before and fooled him. That Joowon only did this because he thought his reactions were funny and not because he liked him. He gets teary and sneaks out.

When he gets out, he realizes that he got a lot of texts from Seunghyun. It just so happens that Seunghyun was behind him. MC cries into Seunghyun's arms and Seunghyun takes him to his house. MC tells Seunghyun that the person he confessed to before was Joowon. Seunghyun asks if he can consider him instead of Joowon. They kiss and are about to do it before they get interrupted. Later, Joowon calls and MC is about to pick up but Seunghyun tells him not to. Joowon is confused/annoyed as to why MC isn't picking up his calls.

Later, MC and Seunghyun spend some time together and they finally do it. MC contacts Joowon's brother and Joowon gets angry that MC is fine and not picking up his calls and is about to drive to where MC is. Then all four of them (MC, Joowon, his brother, and Seunghyun) sit outside eating watermelon. They talk and suddenly the topic of marriage comes up. Apparently Joowon is getting married within the year??? Joowon says it's not true. His father has been urging him to get married.

A little later MC and Joowon are alone and they talk about who the culprit who gave MC a hickey was. Joowon says it wasn't him and MC is flustered thinking it's Seunghyun. They have a misunderstanding where Joowon thinks that MC likes his brother and MC thinks Joowon is calling him liking Seunghyun disgusting. But it turns out it's Joowon's brother who gave him the hickey. Joowon is confused why MC thinks it was Seunghyun. Seunghyun and Joowon's brother comes back and MC tries to chase Joowon's brother to teach him a lesson but Seunghyun holds him back. Joowon looks at how touchy-feely the two of them are and seems uncomfortable.

Later Joowon ropes the MC into a date. MC gets a cut on his knee. Joowon nags at him and says that he worries about him because he loves him. MC is unimpressed and says that Joowon is only saying this because he likes his reactions so he's not gonna react anymore. Joowon says he got caught jokingly but then gets serious and asked MC what he should do to be taken seriously by MC.

Joowon drives MC home and when MC tries to get out at his stop Joowon says he even acted as a chauffeur all day and didn't get anything in return? They kiss. Suddenly, Seunghyun knocks on their window and says he has some side dishes to give to MC's mom. They go to MC's house and Seunghyun lets MC know that he saw them kiss in the car. He is jealous and asks MC how many times have they kissed before? Then MC and Seunghyun do it.

Meanwhile Joowon is trying to call MC but he's not picking up. Then he sees his dad and his dad tells him they need to talk. The next day, Joowon shows up at the field where MC and Seunghyun are working and gives them bubble tea. Joowon drags MC away and tells him to give him his phone. He calls MC's phone and it goes through. Joowon is angry and asks why MC didn't pick up. MC says he didn't realized he called. Joowon tells MC to go to his room tomorrow after tutoring to talk. Then Joowon and Seunghyun have a conversation. Seunghyun asks why Joowon is playing around with MC and Joowon says that he's being sincere.

After MC tutors Joowon's brother, he goes to Joowon's room. Joowon tells him that after the date yesterday, he was going to ask for them to start dating. MC thinks that Joowon is joking at first but Joowon makes it clear he's serious. MC asks if that's the case, why did Joowon do what he did at the field trip. Joowon is confused and doesn't remember. MC is very mad and tells him he has nothing to say to him if he can't even remember.

There's a flashback to when MC confessed to Joowon during the school trip. He sat down next to Joowon and right after he confessed, Joowon said "it feels bad" or something of the sort. MC has some trauma about that. Later, Joowon says that MC likes him too. MC gets mad and says that because he liked him, it was easier/more convenient for Joowon to choose him. He says that they can do it again, but Joowon should never say that he likes him again.

They do it and MC passes out on the bed. In the meantime, there's another flashback about what happened during the field trip from Joowon's POV. Apparently he was sick during the field trip and was so woozy that when MC confessed, he didn't hear him at all and was only focused on trying to call his mom. Joowon tells MC that he has sunlight allergy and it was really bad when he was little. After the field trip, he was confused why MC treated him so coldly.

MC cries and says that if Joowon hadn't tried to hide his pain then such a misunderstanding wouldn't have happened. Joowon realizes that's why MC thinks he's joking when he confessed. He asks MC, now that the misunderstanding has been resolved, can he give him a chance now? MC is about to agree when he thinks of Seunghyun. He pushed Joowon away and says that they can discuss it later.

Then, Seunghyun calls MC and says he's around the neighborhood and asks if he wants to meet. MC says ok. Seunghyun gives MC some macarons and says that he came because he missed him. Seunghyun acts puppy-like and MC says if he acts this way around everyone how can they get over him (? not too sure about this). Seunghyun says how about he only acts this way towards MC now and asks him if MC is falling for him. Joowon calls MC which makes MC think about what happened earlier. He's about to tell Seunghyun about it but Seunghyun asks if he wants to start heading home since it's late.

On the way home, Seunghyun asks if MC has reconcile with Joowon. He asks if it was related to what happened in the past and Joowon's allergies. MC is shocked and asks if he knew all along, but Seunghyun just realized it when Joowon asked him about what happened during the field trip a little while ago. Seunghyun said that he almost didn't want to tell MC, but that would be leaving MC with painful memories about the past and he doesn't want that because he likes MC. Then, Seunghyun asks, since the misunderstanding has been resolved, who will MC choose?