What? My Janitor Dad Is An SSS Hero!

The story

Frozen 12 years saving a city, SSS-rank awakener Atlas returns to find his wife dead and his son Noah hating the father who left. Hiding as a janitor, he shields Noah from bullies until robots bow to him. The old villain returns with a stronger Frost Titan. Father and son fight together; Atlas defeats the monster and comes home for his birthday.