Jiromaru like the rest of his siblings look up to his father Hiro admiring his strength. After running into the Aka-ari Army he showed bravery despite not knowing how to fight tried to protect his siblings and his mother.
After a volcano erupts in Ou, forcing the dogs to flee, Jirōmaru and his family are locked in a mine by Jinemon Kurohabaki until being later released by Daisuke.
A few months have passed since the defeat of Masamune Kurohabaki and Jirōmaru is grown up, but still lacking in fighting experience. When Monsoon attacks Ou, Jirōmaru encourages his father to fight but is escorted away with Reika and his siblings under Gin's orders.
Reika tells the children with her to rest for the night, when she notices a dog coming up the hill towards them. She recognizes him as Nyūdōunsai Sanada and tells him what has happened in Ou.
- Jirōmaru was orignially called Shirojirō (白次郎) when his name first was mentioned in chapter of GDN when first released in Goraku. This was corrected in volume 3 release