There was an untold rule in the house that he would not show himself in front of her until she calls for him, one of the reason why he hid in that closet. When she was out of the house, it was easy for him to do house chores but when she was at home, it gets really difficult for him to do house work nonethless, house work must be done every single day. Even though Mika just transported there, the memories in the body made it as if it was him also up until now living here, taking everything thrown on him. Mika pitied the original owner of the body. No matter how strict his mother was, the person couldn't hate her, he was not able to love her either, rather he pitied her, same goes for Mika.