Itsuwari no Kaguya-kun

Eighteen years ago, a young Aritaka found a child in a bamboo grove and named him "Kaguya." Raised together, Kaguya grew up without any want, thanks to the support of the prestigious Takemitsu family, Aritaka’s guardians. Kaguya adores Aritaka, who has somewhat delicate health and finds him dazzling. However, Kaguya secretly remembers his true name and age, a truth he keeps to himself. One day, Aritaka tells Kaguya that he wishes to give him the family’s ring—a token meant for someone who will become connected to the Takemitsu family…!?

(Source: Gentosha Comics, translated)

Note: Includes 1 extra chapter.