Secretly in love with your best friend's lover

I, Tatsuya, and Momo have been close friends since childhood. I have secretly loved Momo since then but have never dared to confess. Time passed by, and due to being busy with work, I haven't seen Tatsuya for five years. This time on leave, I decided to stay at my best friend's house for a few days. Tatsuya's apartment is quite spacious, not suitable for someone living alone. And as it turns out, he has a girlfriend, and his girlfriend is Momo! The person I once loved is now the girlfriend of my best friend. The truth is ironic, but I can only wish happiness for both of them.

Tatsuya often drinks alcohol due to work pressure. When he goes to the bathroom, Momo comes close to me and wants to kiss me! Momo hates the smell of alcohol the most, so she refuses to kiss Tatsuya. On the contrary, I don't drink alcohol at all, and according to her, my lips are soft, making kissing very pleasant. Unable to resist Momo's cuteness, feelings of guilt towards Tatsuya vanish. For three days, whenever Tatsuya is away, Momo and I stick together, our saliva blending while our mouths are almost inseparable...