YnU sold 371k from what i last remember. it's #5 on the ORICON yearly charts after "Love so sweet" w/ 423k, i think.
YnU was okay for me. i think it's my least favorite A-side, but i still think it's good.
EDIT: KAT-TUN - 88358 (x1.75) = 154,627
awesome first day sales! it's said it's the highest first day sales since ORICON published them.
to compare:
YnU : 69,659
weeeek : 64,068
Ultra Music Power : 47,092