I'm tired of reading romance manga lately but I just love adorable male leads! Preferable not hentai or yaoi.

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Unsure of what exactly makes a male protagonist cute, but assuming you're looking for the short, child-like characters found in shoujo manga, Pandora Hearts, Kuroshitsuji, and Shibatora come to mind, though they're a bit dark genre-wise. Dadadadan. is more lighthearted.

I'm assuming you mean characters who aren't children? Cos there are lots of cute younger male MC's out there, like in Shounen Maid or Udon no Kuni no Kiniro Kemari.

Anyway, for cute teenage boys, I recommend:
Sougiya Riddle
Karneval
Kaizoku to Ningyo
Tegami Bachi
Hakkenden
Coda