A retractable fountain pen that can be used anytime, anywhere just by clicking, and addresses the challenges of cap-type fountain pens. "Curidas" is named after the mechanism of retracting out the pen tip and the coined word of his CURIOSITY. Even though it's retractable, the ink will not dry without a cap. The airtight space of the pen tip storage part is made small to suppress the evaporation of water in the ink.