The naive younger brother, called the "Fanged Ninja". He originally resented Ikazuchi for staying in the shadows for 500 years, idolizing his brother and respecting most of his decisions. But Isshuu took the fact they weren't rebuilding their Ninja school personally until he found the resting place of his father's sword, Kiraimaru. Desiring to rebuild the Ikazuchi School, Isshuu used the blade with disastrous results. But after learning to use the Kiraimaru in a way where his friends wouldn't be harmed, Isshuu decided to rebuild the school after Universal Stealth Group Jakanja was defeated. He was later shown to have feelings for Nanami Nono.
After the Zangyack Empire was defeated by the Gokaigers, Marvelous returned the Ranger Keys to their original owners. Isshuu and his teammates have their powers again. Final Ep.: Farewell Space Pirates
Super Ninpou Running Fang: similar to HurricaneRed's Sky Dash, but instead of galloping in the air, he just runs in the air while grabbing his enemies in his Stag Breaker electrocuting them.
Super Ninpou Fang Lightning: where he shoots a blast of lightning through his head at the enemy grabbing them, then flails them around electrocuting them and sending them flying.
Ikazuchi Sword Thunder Fang Flash: a cross slash attack with the Stag Breaker and Ikazuchimaru. A different version of this attack is where he did a lightning slash attack with the Ikazuchimaru combined with the Stag Breaker.
The KuwagaRaiger Ranger Key (クワガライジャーレンジャーキー,Kuwaga Raijā Renjā Kī) is Isshuu Kasumi's personal Ranger Key and what became of his powers after he along with the rest of the 34 Super Sentai sacrificed their powers to end the Great Legend War.
This key along with the majority of the Ranger Keys were collected by the Red Pirates and later used by the Gokaigers. The KuwagaRaiger Ranger Key was mainly used by Ahim de Famille (Gokai Pink), who used it to fight as KuwagaRaiger.
When the Gokaigers became the Hurricanegers with Gouraigers and Shurikenger while fighting against Basco after Marvelous was incapacitated. Ep. 47: The Limits of Betrayal
After Zangyack were finally defeated, the Gokaigers gave the Ranger Keys back to their rightful owners. Isshuu received his key and became KuwagaRaiger once more. Final Ep.: Farewell Space Pirates
Gallery
A female version of the KuwagaRaiger suit as seen in Gokaiger.
A copy of KuwagaRaiger was created by Madogi as part of the Fake Rangers. Madogi of the Phantom Beast Corps created evil duplicates of the Earth Ninja to draw out the real ones as part of Sandaaru's plan to trap them to lure out Gozen to destroy the barrier he made with the Raging Arrow medal. Though the the fakes were destroyed after this, this was part of Sandaaru's plan to take control of the Hurricanger, Gouraiger, as well as Shurikenger with special collars to force Gozen to feel sadness so he could remove the Grieving Bow medal she possessed from within her body. Scroll 48: Trap and Eternal Life
Behind the scenes
Portrayal
Isshuu Kasumi is portrayed by Nobuo Kyo (姜 暢雄,Kyō Nobuo). As a child, he was portrayed by Shion Tsuchiya (土屋シオン,Tsuchiya Shion). As KuwagaRaiger, his suit actor was Yasuhiko Imai (今井 靖彦,Imai Yasuhiko).
Notes
Isshuu and his brother Ikkou Kasumi are the first Sentai heroes to have an insect theme; comparatively Kamen Rider, Toei's other major Tokusatsu franchise based on the works of Shotaro Ishinomori, were insect-related from the beginning.
Isshuu is the first Sentai hero associated with the deep-blue color of Navy. This is to differentiate him from the main Blue of Hurricaneger.
In the movie Gokaiger Goseiger Super Sentai 199 Hero Great Battle, Isshu's Ranger Key Clone was among the Black and Green Rangers Agri and Don Dogoier were fighting when the Goseigers/Gokaigers were battling clones of the same color/rank, rather than being among the Blue Ranger Key Clones Joe was fighting. Oddly, Ikkou's Key Clone was still among the Red Rangers. If the Key Clones were to fight the Gokaiger that primarily used them, the KabutoRaiger Clone would fight Don, while the KuwagaRaiger Clone would have fought Ahim.
Isshuu is the second ranger to take the place of a Pink Ranger after Tetsuya Yano.
Isshuu is the only member of the team to not officially possess a Karakuri Ball medal in his personal medal's design.
Revolver Mammoth's loading of Kabuto Spear's Karakuri Ball is the only instance where it's indicated to belong to Isshuu, despite the weapon's medal design indicating otherwise.