Ryouko Asuka mentions that she is still feeling tired from the shock during yesterdays bath which was the bath in chapter 149. It is implied that this shock was off screen since the scene in 149 doesn't show any kind of shocking action.
In part 1, Aoi's demon familiar reflects when he was trying to sneak up on her and feed her his manju, and one of the scenes he tries when she is in the bath, though only her silhouette and dish is seen.
In part 2, Hilda wins a raffle to go to a mixed bath for 5 people (plus a night's hotel stay), so the family goes (Beel also comes since children are free) and the 3 main chars go in the pool. The father comes too late.