Well here is the Volume 11 summary as not sure if its been already posted. Am half-asleep right now.
Spoiler for Volume 11:
The Wizard Yū has rejected Sen's Valentine's Day chocolate. He challenges Sen, saying stuff like romantic feelings being in the way of a Wolf's prowess and calling her a coward who has no right to to get a half-price bento. Hana (with the help of Hiroshi Onizuka, the Exorcist) tries to take him on to help Sen but fails miserably and is soundly beaten up. Hana collapses and develops a fever, and is hospitalised. Ume approaches Yō for help to defeat the Wizard, who is currently the strongest Wolf (even the Sawagi twins are weaker than him). Yō accepts, partly because he himself has some feelings for Sen. Ume feeds him some red dates as encouragement (what?). Yō enlists the help of the twins, who managed to uncover a clue to help fight the Wizard in their previous fight against him. He also gets Ren's help (hence reforming Two Dogs once again), as well as make Yū promise to accept Sen's feelings if his team can defeat him (which also happens to be what will be Yū's last fight as he will be leaving Japan the next day).
Yō quits the Half Price club so he can fight Sen (because there's a rule that club members cannot fight each other). Sen refuses to retract the rule so Yō quits. During the fight Ume goes to Sen and tells her as Yō's feelings for her, as well as.why Yō did what he did, after which Sen rushes to the battleground and starts confronting him and asking him to return to the HP club after this fight (she's back to her normal self).
Long story short, Yō wins so he tells Sen to go back to Yū, but Sen, having made her decision after listening to Ume, decides to accept Yō's feelings towards her instead.
Well time for what i got for Vol 12
Vol 12 is an epiloque after the confession between sen and sato. It basically is a multiple ending for you to choose freely as your wish who is going to end up with sato.
There are 6 main heroine for this vol.
Shaga Ayame,
Yarizui Sen,
Shiraume Ume,
Yarizui Marika,
Hirobe Ran,
and Sawagi Kyou
Best i can give you sorry. Now for the visuals.
This is all i can give you and most likely all i will ever be able to find. Hopefully someone else one day will come and expand upon volume 12. I find it amusing i even forgot about the series sadly.