|This article is about a/an episode in Kamen Rider Den-O.|
The Prince's Goodbye Lullaby (グッバイ王子のララバイ Gubbai Ōji no Rarabai) is the twenty-fourth episode of Kamen Rider Den-O. It features the debut of Den-O Wing Form.
After Ryotaro becomes arrested while trying to return Sieg's host, Hana tries to teach the troublesome Imagin what it means to be a real, responsible prince.
After being arrested by the police, Ryotaro is questioned on his involvement with the kidnapping of baby Yūsuke Takayama. During the interrogation, Momotaros, Urataros, and Kintaros attempt to help him, as he has no knowledge of the event. On the DenLiner, Hana and Yuto try to understand what is going on, and Hana tries to talk some sense into Sieg about what he has done to Ryotaro. Hana tells him that a master has to take care of his servants, and with a slap, Sieg develops new respect for Hana and begins calling her Princess. Sieg manages to speak through Yūsuke to convince Shiori Takayama to acquit Ryotaro. Ryotaro is then brought to the Takayama mansion to be thanked, with Sieg possessing him with intent to live the good life forever. However, because he opened a contract with someone with very little memory like baby Yūsuke, Sieg begins to dissolve away. He goes to say goodbye to Yūsuke, but he is interrupted by the Scorpion Imagin's second attempt to bring Shiori to his contractor. Before Yuto can intervene, S-Ryotaro transforms into Kamen Rider Den-O Wing Form, managing to knock the Scorpion Imagin down. However, Sieg's dwindling strength allows the Scorpion to escape with Shiori. Sieg asks Ryotaro to save his mother, as he follows the Scorpion Imagin back in time to February 22, 2002, the day that Akio Masuda was fired by the Takayama family. Den-O fights the Scorpion Imagin as Rod Form and then Ax Form, and defeats him with a Dynamic Chop. Back on the DenLiner, Sieg continues to waste away until Ryotaro returns and shows the Owner a Rider Ticket bearing Sieg's image and the date June 1, 1997, that he got after using a Rider Ticket on Shiori. In reality, Sieg had already fulfilled a contract with the mother, before forging his contract with Yūsuke. Thanks to this, the DenLiner arrives on the day of Shiori's wedding, and Sieg leaves the DenLiner to live happily in the past.
- Ryotaro Nogami (野上 良太郎 Nogami Ryōtarō): Takeru Satoh (佐藤 健 Satō Takeru)
- Hana (ハナ Hana): Yuriko Shiratori (白鳥 百合子 Shiratori Yuriko)
- Yuto Sakurai (桜井 侑斗 Sakurai Yūto): Yuichi Nakamura (中村 優一 Nakamura Yūichi)
- Naomi (ナオミ Naomi): Rina Akiyama (秋山 莉奈 Akiyama Rina)
- Airi Nogami (野上 愛理 Nogami Airi): Wakana Matsumoto (松本 若菜 Matsumoto Wakana)
- Seigi Ozaki (尾崎 正義 Ozaki Seigi): Akira Nagata (永田 彬 Nagata Akira)
- Issē Miura (三浦 イッセー Miura Issē): Ryo Ueno (上野 亮 Ueno Ryō)
- Momotaros (モモタロス Momotarosu, Voice): Toshihiko Seki (関 俊彦 Seki Toshihiko)
- Urataros (ウラタロス Uratarosu, Voice): Kōji Yusa (遊佐 浩二 Yusa Kōji)
- Kintaros (キンタロス Kintarosu, Voice): Masaki Terasoma (てらそま まさき Terasoma Masaki)
- Ryutaros (リュウタロス Ryūtarosu, Voice): Kenichi Suzumura (鈴村 健一 Suzumura Ken'ichi)
- Deneb (デネブ Denebu, Voice): Hōchū Ōtsuka (大塚 芳忠 Ōtsuka Hōchū)
- Sieg (ジーク Jīku, Voice): Shin-ichiro Miki (三木 眞一郎 Miki Shin'ichirō)
- Owner/Opening Narration (オーナー／オープニングナレーション Ōnā/Ōpuningu Narēshon ): Kenjirō Ishimaru (石丸 謙二郎 Ishimaru Kenjirō)
- Akio Masuda (増田 明男 Masuda Akio): Tsuyoshi Muro (ムロ ツヨシ Muro Tsuyoshi)
- Shiori Takayama (鷹山 栞 Takayama Shiori): Kyoko Kano (鹿野 京子 Kano Kyōko)
- Yusuke Takayama (鷹山 祐介 Takayama Yūsuke): Taiga Watanabe (渡辺 虎雅 Watanabe Taiga)
- Police: Kei Tamura (田村 圭生 Tamura Kei), Tareyanagi (たれやなぎ)
- Police Officer: Shiro Namiki (並樹 史朗 Namiki Shirō), Takashi Yamanaka (山中 崇史 Yamanaka Takashi)
- Driver: Akira Shinjo (新城 彰 Shinjō Akira)
- Reporter: Hirohide Koizumi (小泉 博秀 Koizumi Hirohide)
- Servant: Setsuko Kawaguchi (川口 節子 Kawaguchi Setsuko)
- Scorpion Imagin (スコーピオンイマジン Sukōpion Imajin, Voice): Nobutoshi Canna (神奈 延年 Kanna Nobutoshi)
- Kamen Rider Den-O/Momotaros: Seiji Takaiwa (高岩 成二 Takaiwa Seiji)
- Urataros: Eitoku (永徳 Eitoku)
- Kintaros: Jirō Okamoto (岡元 次郎 Okamoto Jirō)
- Ryutaros: Toshihiro Ogura (おぐら としひろ Ogura Toshihiro)
- Deneb: Yoshifumi Oshikawa (押川 善文 Oshikawa Yoshifumi)
- Scorpion Imagin: Jun Watanabe (渡辺 淳 Watanabe Jun)
- Kamen Rider Den-O Wing /Sieg: Naoki Nagase (永瀬 尚希 Nagase Naoki)
- Den-O: Wing Form, Plat Form, Rod Form, Axe Form
- As part of Super Hero Time, this episode aired alongside Juken Sentai Gekiranger episode 20, Lesson 20: Gicho-Gicho! Triangle Opposing Fight.
- Viewership: 6.1%
Blu-ray Box 2 comes with 18 episodes.