hmmm. but no. 6 has a completely different feel and bus gamer was cut before it even started tho?
ao no exorcist, i can give you that. anyway, anime like getbackers... lots of action, no romance, maybe some family... hmmm. have you seen black cat?
Now that you've mentioned it, yea I think No. 6 have different feel but they have the same ingredients. One thing I love about gb manga is the details of scifi (like electric eel for ginji's powers, the missing link, magenjou construction, alternate universes in divine design what not) they're not just product of pure imagination but also research and no. 6 has that, the neoroscience in safu's script. , the no. 6 city is pretty much like magenjou, the futuristic concept. No. 6 city and magenjou's politics have similarities as well. then the friendship of sion to nezumi, though it's like implying more than friendship compared to gb. scifi/fantasy/friendship less romance, they're the same from my point of view.
bus gamer has three anime episodes. though it was just three, i enjoyed it so much

I looked for black cat in mangafox but the manga is licensed. maybe I should watch the anime first. thanks
