ASSISTANCE

i think i have one, one sec

http://www.mangago.me/read-manga/kijima_kun/
more than 30 chapters,don't let the 'latest updates' fool you. It is ongoing though

It's marked as ongoing but it last updated in 2017 so...

I shall check it out, thanks for your assistance

http://www.mangago.me/read-manga/suki_de_gomen/
Not really a SCARY face but is the only one I could think of with about 20 ch (still ongoing).

Hope these are to your liking. Uke with scary face/hard to approach/delinquent or deliquent like types

http://www.mangago.me/read-manga/shishi_mo_kobamazu/
http://www.mangago.me/read-manga/tadatada_suki_to_iu_dake_de/
http://www.mangago.me/read-manga/megumi_and_tsugumi/
http://www.mangago.me/read-manga/shitteru_yo/
http://www.mangago.me/read-manga/oko_sama_star/
http://www.mangago.me/read-manga/kirei_ni_shiteyo/
http://www.mangago.me/read-manga/darkness_hound/
http://www.mangago.me/read-manga/sonna_me_de_mite_kure/
http://www.mangago.me/read-manga/sore_o_koigokoro_to_yobu_no_nara/
http://www.mangago.me/read-manga/heart_no_kakurega/
http://www.mangago.me/read-manga/nirameba_koi/

You are a godsend

Oops. Sorry, I only read the scary uke part and neglected the "max 20 chapters" but I hope you'll enjoy those