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Soredemo Sekai wa Utsukushii (boy is the king of the world and the girl is older who is married to him by arrangement) : REALLY REALLY GOOD :DDDD i heard the anime came out awhile back and the songs were beautiful. but i do prefer the manga.

Get Love : Girl falling for shorter guy. I know this gets ecchi but there is no hentai where they literally have sex (and I think there is one scene but it's like only one page read so you can easily skip and not miss out on the story).

Library Wars : Shorter guy but he's tough...the girl doesn't realize he's her prince LOL. good read though the girl could get annoyingly ignorant on certain things.

Monkey High : Beautiful girl falls for normal "monkey" like boy. nice and playful read.

Fruits Basket : Plenty of cute guys

Romance manga with kids as main leads :

- shugo chara

- yumeiro patissiere

- cardcaptor sakura

- gakuen alice

- kodomo no jikan

can't think of anything else :) but these guys are all cute to the max. younger guys. but some are not younger than the girl.....

Mahoromatic

Loveless

Dance in the Vampire Bund

Daphne in the Brilliant Blue

MM!

Vandread

Gantz

Blood+

Ex Driver