For the female party member, yes. They will wander on their own. You can order them to go to places or attack enemies. For Kota, he has his own lust mechanics which increase every turn. If it reaches a threshold, he will start pursuing the closest available female party member. So your job is to find your own solution to complete each quest. You can order every party member to keep them occupied. You can let them do their own "things". Or you can try to finish the quest yourself but occasionally interrupt Kota's misdemeanor.