The Melancholy of Haruhi Suzumiya, Vol. 11 - manga

Trapped on the snowy mountain by both a storm and the supernatural forces that have cut off Yuki from the Data Overmind Kyon is roused from sleep by Asahina slowly unbuttoning her nightshirt as she climbs into his bed! Kyon realizes it cannot possibly be the real Asahina (darn!) and though he doesnt mind the houses tricks (who would?) he and the Brigade have to crack the code and escape fast before Yukis fever (and Haruhis restlessness) gets out of control!