Jiro is first encountered alongside Saburo in the chamber with the large pile of skeleton in the Sunken Ship during Amaterasu's quest there. Like Saburo, Jiro is also a hermit crab, but his shell is of a green color and the shell on the back of his body is a shark head, which spits explosive urchins in defense of Saburo while she attempts to dig through the ground of the arena and flood it with water. If this happens, Jiro and Saburo would reunites into Ichiro, with Jiro's armor as the shark's head. When the shark head armor is destroyed, Jiro's curved and soft abdomen will be open and vulnerable to damage, but he is still able to throw urchins.
In life, Jiro was the fiance of Saburo, but their marriage was opposed by their parents. Having no other choice, they committed suicide together by throwing themselves into the sea. Their restless spirits possessed the two hermit crabs in the Goryeo and and became Jiro and Saburo. Even when being demons, they still long to be reunited, thus Saburo constant attempts in digging through the arena and cause water to flood in, while Jiro tries to protect her. When successful, they will reunite into the form of Ichiro.
"Jiro and Saburo are the spirits of a couple who jumped into the sea when their marriage was opposed by their parents
Jiro resembles a hermit crab with a shark head for a shell.
It throws sea urchins to protect Saburo and uses its own hard hide for defense.
Attack repeatedly and the shell should disengage."
Immediately when encountered, Jiro will start spitting sea urchins, attempting to protect Saburo so that she can dig and flood the arena. Even when assaulted by sea urchins, Amaterasu has to focus Saburo first, otherwise, when the arena is flooded, they will reunite into the form of Ichiro. After Saburo had been taken care of, focus on Jiro. Carefully approach the male hermit crab, then lash out at him. When his armor has been knocked off, use Golden Fury and the Thief's Glove to farm him. The hidden strike glitch is not necessary, as a Sub-Reflector Counterattack cannot be executed on Jiro. Thunderstorm and Thunderbolt will severely damage him, even when his armor had not been knocked off. It is also his Floral Finisher, so when he is killed, use it right away.