I'm looking for manga like Boku to Rune to Aoarashi, Yotsubato, Barakamon or Koneko Hiroimashita. Something with a teen/adult guy MC with a little kid and focuses heavily on their relationship and their daily lives. Thanks! 🙂

Ooh, one of my favourite themes for slice-of-life manga!

Hiso Hiso
Flat (AOGIRI Natsu)
Boku Wa Ne
Hinamatsuri
Chichi Kogusa
Gakuen Babysitters
Goggle -- The title story only.
Hanaotoko
Hoiku no Ou-sama
Imouto Days
Papa to Arukou
Sora kara! My Nanny
The Children's Teacher, Mr. Kwon
Working Holiday
Papa Told Me
Aishiteruze Baby
My Girl (SAHARA Mizu)
Hotman
Eien no Honey from Hitori-tachi
Ensemble (Yubi)
Usagi Drop, though if you want their relationship to remain innocent, you're in for a disappointment.

Hinamatsuri

Hobbies include impersonating fictional characters and sucking on ketchup packets.

Seconding Chichi Kogusa

Amaama to Inazuma
Baby, Kokoro no Mama ni!
Neko no Machi no Ko
Shirogane no Nina

Oh my! Thank you very much! 😀

@calstine
Thank you very much! I'm glad to hear that you like them too ^_^

@Suxinn
Thanks a lot! Amaama's getting an anime too! Yay!