Nobunaga's Imouto is My Wife

Nobunaga's Imouto is My Wife Summary:

The male student, f.u.kai Nagamasa, ignores
his studies for college entrance exams in favor of following the path to
chuunibyou. As he fainted during night cramming session before the
exams, he realized that he was transported to a parallel world as a
feudal lord in the Sengoku Era. Not to mention that suddenly, he was
marrying the sixth Demon King, Oda n.o.bunaga’s little sister, the one who
was purported to be an unrivaled beauty?
「I’ve decided. I will develop both: this land and the beautiful princess!」
He decides to continue developing his cute, virgin bride night after
night, and to try to live an enjoyable life in a harsh world where magic
and demonic beasts exist.