Sooooo....lets clear up some things with the sexual conflicts of the show, cause it can REALLY get confusing...
-First we have kenshi's infamous "massage" technique, which is given all the girls orgasms, but most dont like the side effects....

-It seems that Flora and Mexiah are the only ones who want to nail Kenshi in the sack, the other girls seem to just be strongly attracted to him for now.....

Question 1- Whats up with Yukine?! She's my favorite girl on the show, but her emotions be SOOOOO out there....does this have to do with kajishima sensei? Like one moment she feels she has to show her naked body to get kenshi's love, but when her naked body actually comes in physical contact with kenshi( which has happened a few times) she gets SUPER depressed, even to the point of breaking down crying....whats up with that?!!?

Question 2- Do you think that Mexiah or Flora have actually had some kind of sexual intercourse with kenshi, cause it is strongly implied sometimes....

Question 3- In episode 6, during the pillow fight, Kenshi slides under Aura and apparently sees her yoohoo, she then talks about she cannot marry now, just cause he saw her vagina?! and what does she mean the responsibility is yours? does she mean for kenshi to marry her or impregnate her?

It something that occurs in a lot of anime, what appears to be a very old tradition that if a woman is seen naked, she's no longer pure and can't get married to anyone else. Mostly it shows up in comedy works, since it's not taken seriously any more.

About Yukine, I think her bipolar moments happen because the time she offers up her body she mentally prepared for it but when Flora disrobed her and shoved her onto Kenshi, she wasn't ready and broke down crying. Adorable. =3

I can only think of one time 'offered herself up', and that was when Maria-hime told her to do so, in order to gain control of Kenshi-san. Did it ever happen again?

Oh yes. She's attracted to Kenshi-san, but she's also very shy about it. She wasn't happy with the plan, and especially not with getting stripped in front of him at the party.