"The jewel mounted on this ring is actually a tiny compartment used to store medicinal capsules."
— Item description
Capsule Ring (カプセルつき指輪 Kapuseru-tsuki yubiwa ) is a special item that can be found in the "end of the road" scenario.
The Capsule Ring appears at the top level of the Drainage area just before Tyrant R appears. It only appears in the HARD difficulty level.