Happy Damun Buldonkatsu & Gimbap is a 24-hour restaurant near Gangnam that serves gimbap, donkatsu, and sundubu. It offers buldonkatsu and mixed gimbap, and its donkatsu sauce is a demi-glace base with a separate secret addition. Order at the entrance kiosk or at your seat, and get water yourself. The shop was already old in 2014 and was renovated around the time of COVID.