Read Three Years Apart manga
Mizuki and Kazuya, childhood friends, are 3 years apart.
It’s not really a so-called “Age Gap” but that makes some distance between them during their youth.
From their childhoold to the present, story will be told about these two who are 3 years apart.
Artist’s Pixiv: https://www.pixiv.net/member.php?id=596062
Artist’s Twitter: https://twitter.com/shimazakikazumi