2-sai Sa no Osananajimi

He was just a childhood friend, like a cute little brother.
But now, six years later, he is……
Even before we started dating, and now that we are going out, I can still feel my heart getting all flustered.

(Source: ComicWalker, translated)

Note: Originally self-published by the author, it was collected for commercial tankoubon release starting on 2023-02-10.