 If you liked
Lamune
|
 ...then you might like
ChäoS;HEAd
|
both series are harem type anime with one male protagonist and 6 female heroines. plus both female leads rimi sakihata and nanami konoe are both romantically linked to the male leads takumi nishijo and kenji tomosaka, plus both male leads have one of the 6 heroines as a sister (nanami nishijo and suzuka tomosaka)