Dokuzetsu no S na Ore ga Jimi Riman ni Kuwaresou desu
Shirouto Yankee Kikiippatsu!!
He fights in the street when a stranger saves him. To repay him a ask the stranger what he could do for him. The stranger is actually a porn actor. He ended up in a porno and they discovered that they're body is compatible. They are in love I guess.
Nyaa to Nakukara Aishiteyo
One day while being very drunk he picked a stranger thinking it was a cat. He wakes up and realizes is mistake. They actually keep in touch. One day the cat stranger gives him a blowjob to show his gratitude. The stranger is actually an alpha and not an omega. He just loves sex.
Dakaretai Otoko Ichii Ni Odosarete Imasu.