 If you liked
Durarara!!
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 ...then you might like
Zankyou no Terror
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If you like anime set in cities and smart characters who like toying with people, Durarara / Zankyou no Terror is the way to look. Both also have that fun and seemingly playful character who has had darker times, and even a shy girl if that's what you're looking for.
Aside from the sense of mystery, the art style is admittedly similar at points- You have that 'online' element though with Durarara it is with chat rooms, as well as beautiful night scenes with buildings and cars motorbikes. There is also rivalry for its fans, and potential ships as a bonus.
It tends to give off a similar vibe. Both follow connections of crime and the semi-supernatural through a cast of very unique characters, including a main trio of "mastermind protagonist, enthusiastic and extroverted best friend with a dark past, and quiet girl with lots of potential who frequently faces harassment"