Volume 4 features the revelation of Suzu's past career as an Idol singer! Then there is more abuse of Chitan, then the obligatory Valentine's Day chapter (fear the guy with the chocolate heart sticking out of his rear...), a fishing trip, Chitan the rock star, and a little super-shoujo Oniisama E parody ^_^
The chapter titles are:

1: Nishi kara Kita onna!!:
2: Katokubu bushitsusou datsusen:
3: Otoko no Valentine!!: Boys Valentine!!
4: Bigin za Bidan!!:
5: Shinu made tomaranai!?: Unstoppable until Death!?
6: Hina matsuri ni ikou?: Going to the Girl's Festival?
7: Hiikomono gatari: Favorite things Story
8: Konan de iiwake?: Difficult Explaination?
9: Wasureta tomo!!: Forgotten Friend!!
10: Fukkatsu no Dorama-: Restoration Drama
11: Kibun wa jyouryou kaikyuu!!: The Feeling is Upperclass!