Sefure Ga Dekita Riyuu — Boku No Harem

This title is associated with adult-oriented romantic comedy / harem stories, often found on sites like Shōsetsuka ni Narō (Let's Become a Novelist) or similar platforms for web novels. The plot typically involves a protagonist who unexpectedly ends up with multiple casual intimate partners (セフレ sefre = sex friend / friends with benefits), exploring the circumstances or misunderstandings that lead to that situation.

(ぼくのハレム・セフレができた理由), which roughly translates to "The Reason I Got a Harem of Casual Sex Friends." boku no harem sefure ga dekita riyuu