Nanbaka x Male reader (Zombie apocalypse edition)

What would happen if a zombie apocalypse broke out three years ago in Japan and across the world?

You, your brother B/n, and his twin sister Aria have survived on your own since the apocalypse began three years ago. You were 18, while your brother and sister were 14 years old when the apocalypse happened and now you're 21 while they're 17. You and your siblings were able to escape school when the walkers came into the school. You taught and raised your siblings everything you could and promised yourself to protect them when facing challenges.

At Nanba prison where the guards and inmates have survived with the government giving them food, water, clothes, weapons, electricity, and etc. After three long years of Nanba surviving, the government ordered them to go out and find the survivors while they find to cure. What would happen if Nanba found out you're immune to walker bites?

hint- The Nanba character's ages are still the same age in the present day but younger when the apocalypse started.

I don't own the Nanbaka characters, pictures, etc.