The Tachikawa School G Sepia Ink is refillable, fast drying waterproof, & Copic-proof. It's great for calligraphy & manga/comic creation. *This pen is intended for frequent use & can dry up if left unused for 1–2 weeks. If the pen does dry up, soak the tip in water to revive it. *When installing the ink cartridge, keep the nib of the pen facing downward.