MC makes love with his step sisters (so sister tag added but not incest).

Base +10

[エムビーエストゥルース チェリッシュピンク] 姉（×2）・オレ・妹～教師、同級生、後輩のカンケイ～
[MBS Truth -Cherish Pink-] Ane (×2) Ore Imouto ～Kyoushi, Doukyuusei, Kouhai no Kankei～

Release date: 2004/06/25

Link (VNDB): https://vndb.org/v1699
Link (Wikipedia Japanese): http://ja.wikipedia.org/wiki/MBS_TRUTH#Cherish_Pink

Base +17

Getchu: http://www.getchu.com/soft.phtml?id=43330
What they don't tell you though is all of them have off-putting traits (the blonde is arrogant, the redhead's a lush, the orange haired one smokes tobacco, the blue haired one is a brat, and the purple haired one drinks and is mean.)

Base +7