Ore no Koibito no Hanbun wa Junjou de Dekiteiru

This is the story of the relationship between college students, Yoshiyuki who is living with his tsundere Lover, Yuzu. Yoshiyuki wants to take it a step further with Yuzu, but due to Yuzu's naive personality, one simple kiss makes him look like a boiled octopus. With dreams of days filled with naughty things, Yuzu makes a "certain promise" with Yoshiyuki during their first month of dating.

(Source: Solmare Henshuubu, translated)