ラブキッズ!! [Love Kids!!]

高校生のリンとキヨは、幼稚園のころからの幼馴染み。お互い知らないことはないくらいずっと一緒に過ごしてきた。
父親の恋人・高橋くんに長年、想いを寄せていたリンは、二人の幸せを願い、この恋を諦めることに。
失恋の悲しみをキヨに慰められ、立ち直ったリンだが、キヨから突然「好きだ」と告白されて…!?
思春期を迎えた二人の、青春ラブストーリー

From Mangaupdates :

High schoolers Rin and Kyo are childhood friends from kindergarten. They're so close that there's virtually nothing they don't know about each other.

Rin, who had been pining for Takahashi-kun, his father's lover, for many years, finally gave up and wished for his father and Takahashi's happiness. After his broken heart was comforted by Kyo, Rin was finally able to stand up again, but then suddenly, he was confessed to by Kyo...?!

Sequel to Koishite Daddy, focusing on Rintarou, the child from the first book, now that he is in high school.

Related Series :

Koishite Daddy (Prequel)
Love Limit!! (Sequel)