I Kept Pressing the 100-Million-Year Button and Came Out on Top, Vol. 3 (light novel)

When Lia’s father, the King of Vesteria, discovers that Allen has been living with his
daughter, he invites (nay, orders) both of them to his domain. There, the
overprotective King shocks Allen with a bold decree: “If you want our daughter, then
prove you are the strongest in Vesteria!”