 If you liked
Shakugan no Shana
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 ...then you might like
Monochrome Factor
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Both have lots similarities, like the disappearance of people, in Shana people totally forgets about you under certain circumstances and in this one is through the lose of your shadow. They both set an alternate version of the real world for battles and both even have a Tsundere relationship between the main characters. If you like one for the comedy and battles formula, then you should give a try to the other too.