It is catchphrase of character [[okada akane]] in response to her imagining about [[nemoto hina]]
It comes in 2 variety
1 the initial one was when Akane shocked for the first time and immediately shout ひな――――――!!!
2 the next appearance in manga was when she saw dildo in sex toy store where she says Hina’s name (ひなぁ...) while having empty eyes
hinaa (reaction face)