Interested in him with 気がある

Grammar Explanation

ふらいんぐうぃっち » Volume 5 » Page 57

Makoto and her family head out on a trip to the river. When they stop to pick up Kei’s friend Nao, Akane greets her with, “Howdy, Kei’s girlfriend!” Nao tells her she’s wrong.

“Yo, my girlfriend.”
“Stop that!”
“Although you say that, you’re interested in him, aren’t you?”