Protagonist "Kariya" transfers to Tokyo's Tsukiyo High School due to parents' job relocation. To fulfill childhood friend's desire to write romance novels, helps collect material at school. Gradually grows closer to "research subjects" through various interactions...

...However, shortly after starting a relationship, realizes fading affection for current partner while developing feelings for someone else. Will you stay loyal through the relationship's rocky phase, or succumb to temptation in this increasingly twisted love triangle?

[From Steam]