Runa is all cuddled up against Blake, he turned Panther to be nice warm and soft
but he is afraid that moving to much (like getting up), making a sound or transforming back will wake her up
plus if he transform now, Keela will see him nude and if Runa wakes up then she will as well (and possibly accidentally touch him)
He is kinda shy to transform where others are watching (which if kinda funny since he needs to be nude to transform or risk destroying his clothes and having to walk panther like or all nude until he gets replacements XD)
trough on the other hand he has seen both of them in their eva costume, so in a way its only fair (aside the accidentally touching risk, And Keela has no idea he was their silently when she was getting out of her bath soooo.... in that way it would be weird to explain about the fairness part (which I can see he might slip when reacting to Keela her possible reaction)
anyway, long story short, due to varies reasons and possible situations, he cant move or transform unless risking chaos with the girls, as waking Runa.
I think he is going to be acting like a big brother for her ^^