[Hayake] A Cool Little-Girl's Inner Heart (COMIC LO 2023-10) {Mistvern}

Sayo, a deadpan bookworm who treasures her library reading time above all else, has a quiet arrangement with her teacher: after closing time, he gets her squishy little body and she gets to keep her book open. The usually meek girl turns shockingly bold once they're alone, sucking him off like a piece of candy and slamming her hips down cowgirl-style while her cool expression never cracks, no matter how much her sensei rambles about how adorable she is. What starts as a library trist escalates into an entire day spent together, but back at school the two struggle to keep their secret when Sayo's blunt mouth nearly blurts everything out.