Short stories about Yuu, his vigorous childhood friend, and their mutual love. The volume release comes with other similar stories made by the author, most (if not all) of which can be found in their Pixiv.
Jitsu wa Ryouomoi Kamo Shirenai Onee-san to Chuusan Danshi no Hanashi is a completed manga by Saisou. It blends romance and comedy. You can read all 10 available chapters of Jitsu wa Ryouomoi Kamo Shirenai Onee-san to Chuusan Danshi no Hanashi online for free on MangaPulse; the newest is Chapter 10, added 2020-07-25. The series is finished, so you can read it from start to end in one go.