Tokidoki, Sekai wa Utsukushii

[from Fantasy Shrine:] High School Senior, Yokozeki Haruhito has always been watching the teacher-in training, Arisawa Yuya. However, this doesn't go unnoticed by Yuya's cousin, Yuma. Yuma volunteered to be Yuya's substitute. Things started to escalate when one day Yuya walked in on them while they were kissing...