Yuki is clearly NOT loli O_o

It's not "clearly" at all.

"Tag what you see, not what you know."

She is if she's drawn that way. Actual age does not apply. End of discussion.

Well, it doesn't look very loli to me.

It looks dubious enough that it could go either way, here. No breasts, no discernible hips, no pubic hair... generally, that's the body of a prepubescent girl - a.k.a. "loli".

The saving grace here is that in this position it's hard to get a concrete view of what her figure is actually like.