I don't know any backstory about them, but they seem like a cute pairing UwU
P.D : It would be great if someone can translate "AkiNana's Lewd summary" it's a short doujin from the same author, lewd but cute and very enjoyable
^ They're more of a crack pairing, they don't really have any shippable moments, and their dynamic is completely different than what Chiwa's fanart portrays.
Also, i made this suggestion before, but Chiwa and Naga are the same artist, it'd be really cool to get that fixed.