The Personal Circumstances of the Twins.

Synopsis

Kouki and Nao Fujiyoshi are twins who both have a big secret: they are in love with one another. Naturally, they would suppress their feelings due to being brother and sister. However, their mother accidentally reveals that Kouki is actually adopted! Ever since learning that they are not related by blood and put under the impression that the other still views them as a sibling, Kouki and Nao have no idea how to handle their long-hidden feelings. As the twins accept this new circumstance, their relationship suddenly changes, slowly bringing the two closer together than they were ever before. [Written by MAL Rewrite]

Anime adaptations