Ai no Ondo wo Oshiete yo
愛の温度を教えてよ · あい の おんど お おしえてよ
est. Rough estimate based on volume count, reprints and magazine — not an official figure
Overview
Kai spends his days as a sugar baby. One day he's saved by Yuuma who happens to be around while he was having an argument with a client. Kai immediately notices Yuuma's refined appearance and kind spirit, and asks him to be his "sugar daddy. Surprisingly, Yuuma, who's eager to experience new things, accepts Kai's proposal. As time goes by, Kai starts feeling attracted to Yuuma, who, unlike his other "daddies," respects him and takes care of him. Despite these acts, there's a reason why Kai can’t fully trust him... (Source: Core Magazine, translated) Note: Includes one extra chapter.
Source: AniList
External databases: AniList
How to compare editions, collected volumes and ISBNs / Sources, updates and corrections