They run into Earth Dragon (looks like giant turtle), making her freaks out because oh shit a boss monster.
His stupidity makes him immune to its MENACING aura.
Also turn out his battle axe is actually a magical weapon that auto-repair itself (and can repair faster if he wills it to), he got it as spoil of war after killing an enemy general.
He manage to kill the Earth Dragon in a "YOU WILL NOT TOUCH MY WAIFU" moment, which basically broke her love meter and made her confess to him in tears.
The elder convinced him to just get engaged/marry to Aruna, because there's no way in hell any woman would be willing to ignore such a MANLY man who can hunt a mother fucking Earth Dragon.
So he agreed, though when he heard she's 16, 2 years younger than the legal marrying age in the empire, he got flustered for a moment, then decided to just work hard until she's of-age.
Then we must interrupt the fluffy oni waifu life with PLOT, as the 3rd princess show up trying to recruit him into her faction.
Not surprisingly, she left enraged when he refused the offer, and Aruna who's hidden nearby came out to tell him that of the 5 people who came, the princess and her bitch knights are basically super red, the other knight I forgot but maybe white, and his old subordinate is blue.
(tl;dr is there's a war over succession about to happen, bitch princess came thinking she can get funds from him or some more soldiers, but he got nothing because the officials embezzled the money supposed to be given to him)
His old subordinate later returned and join his fief, because he knew when the civil war start he'd get sent to the frontline again so fuck that.
(The made him a spear with the Earth Dragon's materials)
Soon after he get to adopt 2 loli elves, because of course.