Please

Uncle Cool

http://www.mangago.me/read-manga/uncle_cool/ (▰˘◡˘▰)

Can you suggest something like where the guy is actually clumsy or not very handsome ( in the story )

With Age Gap ? I could look but no promise uwu

Yes. With age gap

Hmm on it~

http://www.mangago.me/read-manga/faster_than_a_kiss/ -
More like happy go lucky personality rather then clumsy ╮(￣▽￣)╭

Not all are ten years, but I will go as close to ten years as I can. Note that a lot of them are people with kids since I took a lot from my lists.
Gokusen (8 years), Faster Than A Kiss (8 years), Omukae Shibuya-kun (7 years), My Mother And The Game-room Guest (6 years), Kyou Mo Uchi De Machi Awase (9 years), Love So Life (9 years), Hakuji (I don’t remember but it was enough to make me uncomfortable).

Tysm