Kenja wa Nemuru新城未明の宝石事件簿 賢者は眠る; 賢者は眠る―新城未明の宝石事件簿; A Wise Man Sleeps; Kenja wa Nemuru - Shinjou Mimei no Houseki Jikenbo

Summary from Go! Comi: Miharu hasn't been having a good year. Her mother died, leaving her only a single ring to remember her by, and her father went bankrupt – leaving her with all his debts! Though she intended to sell the ring to pay off her debts, a run-in with a hot boy and a brush with alchemy leave her unable to part with it...literally!