From Yen On:
There's no such thing as too much preparation! The fate of the S-ranked world Gaeabrande rests with the novice goddess Ristarte. As she thumbs through the piles of duller-than-dull résumés for potential Heroes to summon, she hits the jackpot with Seiya Ryuuguuin, whose stats are so high for a level-1 Hero that he's practically cheating. (He's also pretty easy on the eyes.) But there's a catch. Seiya is cautious to a fault.
If he goes to a weapons and armor shop, he asks for three sets of armor: Ane to wear, a spare, and a spare for the spare. Just in case. He always buys ridiculous amounts of supplies, trains like he's racing to max level, and won't hesitate to use his strongest skills even on a simple slime. With a Hero like Seiya on the job, which will run out first-the Demon Lord's forces or Ristarte's sanity? The tale of the overpowered yet overly cautious Hero and the goddess who can't decide if she wants to kiss him or smack him begins.