This is a pretty obvious reference to the fact that tomoyo from clannad and isako from dennou coil are voiced by the same seiyuu. But im not sure if it would be apropiate to add the clannad tag to this image.
I'm wondering whether the houko_kuwashima tag should be kept. It's nothing to do with the art other than the fact that the two characters depicted are voiced by the same person.
Not really much to do with the art itself IMO.
Regarding the inclusion of the clannad tag, I think it should only be included if the character name is also included, which makes sense.