Some articles on jin jakka:
Bountos - Non-Soul Reapers - Zanpakutō Spirits - Ryūjin Jakka
... Ryūjin Jakka is a Zanpakutō owned by Genryūsai Shigekuni Yamamoto ... Unlike the other Zanpakutō spirits, Ryūjin Jakka doesn't have a solid form and is mostly seen as intensely hot flames ... When Muramasa freed Ryūjin Jakka from his Zanpakutō form, it prevented the other Soul Reapers from following Muramasa until Tōshirō Hitsugaya and Hyōrinmaru ...
... Ryūjin Jakka is a Zanpakutō owned by Genryūsai Shigekuni Yamamoto ... Unlike the other Zanpakutō spirits, Ryūjin Jakka doesn't have a solid form and is mostly seen as intensely hot flames ... When Muramasa freed Ryūjin Jakka from his Zanpakutō form, it prevented the other Soul Reapers from following Muramasa until Tōshirō Hitsugaya and Hyōrinmaru ...