what manga is the couple on the left from? http://www.mangago.me/read-manga/kuroneko_wa_...

Looks like akira norizaku manga or ike reibun.. Not really sure. :) thats if you mean the pair at bottom left.

thank you! :)

The 2 at the bottom are: Trigger by Akira Norizaku http://www.mangago.me/read-manga/trigger/
and Bi no Isu by Ike Reibun http://www.mangago.me/read-manga/bi_no_isu/

the couple on the bottom left is from a manga by the same author as heart strings and trigger. and the couple on the bottom right is from bi no isu incase you're condering