If you're looking for manga similar to Dia Game, you might like these titles.
Tempted by an internet advertisement for a "Necoco" doll series, Eiji orders one on a whim, imagining a moe-tastic hadaka-apron-wearing girl to show up on his doorstep. Instead he gets a scrappy looking boy, and to make matters worse... he's an aggressive, tough-talking little brat.
In a world where humans and demi-humans coexist, Kou is a half-vampire, half-werewolf who has been shy of people since an incident in his childhood. "I don't want to get close to people because they look delicious!" After reuniting with Itsuki, the childhood friend of the person who caused his trauma, Kou's daily life changes completely... even though his instincts are sounding the alarm...
I will find a lifelong partner before I go into heat! With that determined thought the young and innocent werewolf Setsuka sets out from the remote countryside to Tokyo. He is quickly scouted as a host, but the owner of the club is werewolf's worst enemy, a vampire Nagato!
Chigusa is a businessman who lives alone. One day he picks up a dirty hairball-like animal, thinking it’s a cat. He washes and feeds it and puts it to bed, but the next morning… in the room there’s an adolescent with cat ears and a tail, which Chigusa has never seen before. He calls Chigusa “Master” and wants to serve him hard, so Chigusa names him “Kedama (hairball)” and they start living together, but…
One day a mechanic finds a child with horns fainted in the mountain and brings him home. So begins their life together.