 If you liked
Kanojo to Kanojo no Neko
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 ...then you might like
Kanojo to Kanojo no Neko: Everything Flows
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Both anime cover the same "Kanojo to Kanojo no Neko" story. "Everything flows" is in color, was made more recently, and has a much longer runtime (still an OVA, though). The other version is 1/6th of the runtime, black and white, and pretty much the first publicly praised work of now famous director Makoto Shinkai.
The story and mood are similar, I give Shinkai's version a slightly better rating because it has more emotional power and better art (even if it is B/W).