Oohashi to Miyake no Baai

Initially, Miyake entered a physical relationship with Oohashi as a stand-in for Takeda, Oohashi's crush. However, over time, they started living together and became more like a couple. Oohashi, who is anxious and tends to be overprotective, has grown increasingly possessive of Miyake—enough to ease Miyake’s own anxieties. Meanwhile, Miyake continues to update his “Oohashi Observation Notebook” in proportion to the time they spend together.

(Source: Ichijinsha, translated)