Last name first then Given name.

MC

Nai Akitsu

-Our Mc of the story have a broken system(not the OP one but literary broken sometimes give him good luck but MANY times give him bad luck) Know some character he met but somewhat forgot his past life and memory because of naming his system late.

Harem At The Moment.

Nai Shiro(little sister)

-A very clingy little sister will follow our mc whenever he go because of fear that he will gone like their parents.

Doma Umaru(step-sister)

-A somewhat cheerful lazy sister that is also very clingy to our mc.

Himiko Toga(Big Sister of Umaru)

-After our mc saved her along with her Sister from the robber he become more affectionate with our mc and act as a guardian(wife hehehe) for them. also Friend of their parent despite younger than them.

Tachibana Marika(Childhood Friend)

Their parent are friend so sometimes they visit the Tachibana's Household They promise to marry each other but our mc forgot it.

Kosaki Onodera(Childhood Friend)

-Their Parent are friend so sometimes they also visit Kosaki's household Along with Marika They also promise to marry each other

Other Character

Nai Jirou(Dead)

-Died when our mc are 8 years old and shiro 7 years old because of unknown phenomenon.

Nai Najenda(Dead)

-Died alongside his husband from unknown phenomenon

Sebas(old man next door/master at martial arts/teacher)

-A kind old man but also the teacher of our mc father and also teach our mc from a very young age. But always dissappear for unknown reason.

Tsuare(Old version)(Sebas wife)

-wife of sebas a kind old woman along with sebas they also dissappear for unknown reason.