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
what manga is the couple on the left from?
http://www.mangago.me/read-manga/kuroneko_wa_shippo_de_amaeru/bt/254518/Vol1_Ch5/3/