 If you liked
Ane Naru Mono
|
 ...then you might like
Hachigatsu Kokonoka Boku wa Kimi ni Kuwareru.
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They both contain a onee-san type character, that is not human as the female protagonist, which look after the MC. Both the female MC can also be counted as borderline obsessive. They also have very similar art sytle (clean & detailed). However, Hachigatsu is much more plot heavy while Ane Naru Mono is more slice of life-es.