Can someone explain to me why there is so much art of Junko biting Reisen's ear? Is Junko's favourite food rabbit? I'm new in the Touhou fandom, so I don't know everyone's lore.

Enderice said in comment #2633130:

Can someone explain to me why there is so much art of Junko biting Reisen's ear? Is Junko's favourite food rabbit? I'm new in the Touhou fandom, so I don't know everyone's lore.

Junko mentions Reisen "caught her fancy" in LoLK. That's all the fandom needs to ship those two. And since Junko is literally crazy the relationship is usually portrayed as being a bit... unhealthy.

Also Junko has a fox motif and foxes eat rabbits, so...