Two rather sweet Hyakko doujinshi by circle Energia (えねるぎあ).

Credits for Tora Heart go to Yutanpo from /a/, and anonymous Japanese PD user(s) for Tora to Uma to no Aida ni ha.

Tora to Uma to no Aida ni ha: http://doujinshi.mugimugi.org/book/327474/Tora-to-Uma-to-no-Aida-ni-ha/
Tora Heart: http://doujinshi.mugimugi.org/book/327477/Tora-Heart/

Remaining doujinshi by the same circle unfortunately shall remain hidden in the depths of the internet.