Yes, he isn't, but this
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Is Kyou speaking at his sister, not her asking him why he's being gross. I think this is where your confusion is stemming from.
>"he's" not grossed out
Unless I'm missing something, he's the one saying this at his sister on page 8, and she has a clear face that could imply revulsion, or being grossed at her brother's sudden "cutesy" attitude over wanting to buy matching things for Yamada.