Shibatora not romance manga but he is the epitome of a fake shota.

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I think chocolate vampire fits this category, though the ml has like a dark undertone but his feelings for out MC Is really cute and genuine (pure on the other hand.... Well you will understand if u read it). The MC is a bit of a bitc- I mean tsundere tho. I too am on a quest to find fluffy cute Male leads that arent underage or look like Naruto with a different hair colour (which unfortunately most shounen protagonists do 😢 ) some of the others recommend are really good aswell, I especially agree with soredemo sekai wa utskushii, it's one of my favourites!

Miageru to Kimi wa is not a shoujo but romance nonetheless and I think it somewhat fits what you're describing.
Anedoki is a shounen manga that has age gap but not too large, and its cute! but if you can't handle ecchi than don't bother with it since its textbook ecchi stuff.
Sincerely: I Became a Duke's Maid is another not-too large age gap but would make you feel quite guilty reading it nonetheless. It's isekai trash but I still love it. This one is properly shoujo but a Manhwa not a manga.