|This article is about a/an episode in Juken Sentai Gekiranger.|
Fortieth Lesson - Head goes Bakān! The Shock of the Truth (修行その40 頭、バカーン！衝撃の事実 Shugyō Sono Yonjū: Atama, Bakān! Shōgeki no Jijitsu) is the fortieth episode of Juken Sentai Gekiranger. This episode reveals the truth about the origin of Jan Kandou and the ascent of Rio into his Genjuken form and position as their "Mythical Beast King".
The emergence of Phantom General Suugu's identity leads to a startling realization by Rio and a shocking revelation regarding his connection to the Gekirangers.
While Gou goes looking for him in the woods as they were looking for mushrooms, Jan finds Suugu playing an ocarina and feels a "Wafu-Wafu" from him. Jan attempts to befriend him, but Gou arrives and battles Suugu to Jan's dismay. Gou is shocked to find that Suugu's fighting stance is the same as Dan, a Beast Arts master who both he and Rio learned from in the past. At SCRTC, Xia Fu cannot believe that Dan still lives as he was killed by Rio long ago. However, Long reveals to Rio that he revived Dan as a puppet that would serve only the Gen Jū King, with the masterless Suugu going on a berserk rampage. He overpowers the Jūken giants single-handedly before being defeated by SaiDaiGeki Fire as Rio arrives before the team, revealing that his battle with Dan had not truly ended. On the night Rio was to end his rivalry with him, Dan was already gravely wounded prior to the fight, thus Rio was robbed of a true victory. A dying Dan tells Rio that his true rival is one who will defeat him: Dan's own son, Jan. Jan is horrified and confused of this new information as Suugu attempted to kill him. Though the others attempt to keep Suugu from killing his son, Jan expresses his feelings about family while taking Suugu's beating until Rio emerges in a new form, embracing his destiny as the Gen Jū King. The four Gekirangers battle the Mythical Generals, only to be overpowered by them before Rio blasts them, allowing Jan time to train for their final confrontation. Rio and his group take their leave, with the war between the Geki Jūken and a fully-powered Gen Jūken beginning as Jan is now in a state of utter pandemonium.
- Jan Kandou (漢堂 ジャン Kandō Jan): Hiroki Suzuki (鈴木 裕樹 Suzuki Hiroki)
- Ran Uzaki (宇崎 ラン Uzaki Ran): Mina Fukui (福井 未菜 Fukui Mina)
- Retsu Fukami (深見 レツ Fukami Retsu): Manpei Takagi (高木 万平 Takagi Manpei)
- Gou Fukami (深見 ゴウ Fukami Gō): Riki Miura (三浦 力 Miura Riki)
- Ken Hisatsu (久津 ケン Hisatsu Ken): Sotaro (聡太郎 Sōtarō, Sotaro Yasuda)
- Master Sha-Fu (マスター・シャーフー Masutā Shā Fū, Voice): Ichirō Nagai (永井 一郎 Nagai Ichirō)
- Miki Masaki (真咲 美希 Masaki Miki): Kazue Itoh (伊藤 かずえ Itō Kazue)
- Rio (理央 Rio): Hirofumi Araki (荒木 宏文 Araki Hirofumi)
- Mele (メレ Mere): Yuka Hirata (平田 裕香 Hirata Yuka)
- Bae (バエ Voice): Akira Ishida (石田 彰 Ishida Akira)
- Long (ロン Ron): Naoki Kawano (川野 直輝 Kawano Naoki)
- Sanyo (サンヨ San'yo, Voice): Hideyuki Umezu (梅津 秀行 Umezu Hideyuki)
- As part of Super Hero Time, this episode aired alongside Kamen Rider Den-O episode 43, Something Missing.
- This is the second of seven consecutive episodes where the character themes (as sung by the actors themselves) make up the ending of Gekiranger in place of regular ending theme Tao. The second, Run, is performed by Mina Fukui, who portrays Ran Uzaki.
Juken Sentai Gekiranger Volume 10 features episodes 37-40: Lesson 37: Gyan-Gyan! Useless Arranged Marriage Discussion, Lesson 38: Biba-Biba! Another Retsu, Lesson 39: Uro-Uro! The Children Don't Return, and Lesson 40: Head goes Bakān! The Shock of the Truth.