Geez, I wonder why "tiger" would have wanted to spike Sensei drug and make her unconscious, whatever could have been the reason?
I'm guessing that MC is superbuffed under the clothes or decided to go for a tactic to use clothes to dampen the damage, or maybe weights under it.
Would be interesting if he and Sensei use a tactic to make tiger believe they are a couple to make him blind with rage and jealousy.