YUUSHA PARTY WO OIDASARETA SHIRYOU MAJUTSUSHI WA LICH NI NATTE MAOU-GUN DE DAISUKINA KENKYUU LIFE WO OKURU

Yuusha Party wo Oidasareta Shiryou Majutsushi wa Lich ni Natte Maou-gun de Daisukina Kenkyuu Life wo Okuru summary:

It was believed that the most powerful necromancer in the brave party died in battle and was left for dead.
But he wasn't dead.
He was resurrected as a "Lich", a being "physically and magically the strongest", and decides to leave the human race and live with the demons - the demons were richer and he could learn necromancy more freely! With Alice, one of the six demon generals, as his partner, the Lich plunges into his research.
Will the Lich be able to live the quiet life he has always dreamed of without the interference of adventurers?