Three Delinquent Girls Spit in My Face, Then Become My Girlfriends for Life

[No AI + heroine pursues hero + subverts expectations + nation, family, and martial world + boyfriend by contract] After the campus beauty and her two best friends drenched me, I somehow ended up as their boyfriend for life under a contract. My old enemies steered clear of me, and I wouldn’t dare touch my old engagement. I planned to do the laundry and cooking as a decoy, then live out the rest of my days in peace. But life kept pushing me forward, Who could have guessed that before long, I’d become a defense envoy guarding the borders of the Nine Provinces?