0 damage assassin

Peeping into woman changing room without noticing, easy. Walk to royal treasury, simple. Scout unknown and dangerous areas, manageable. Finding hidden places and treasures, it happens. Escaping embattled situation, it is possible. This is story of assassin known as "No-one". He has two problem. He can deal only zero damage with his weapons and he can´t take a single hit. How is he going to survive?

Picture isn´t mine. It is illustration from "to be a power in the shadows". I changed picture to manga one for a while.