|This article is about a/an episode in Kamen Rider 555.|
Friend or Foe? (敵か味方か Teki ka Mikata ka) is the thirteenth episode of Kamen Rider 555. It is the fourth and concluding episode of the Kaixa Gear arc, culminating with the debut of Masato Kusaka, and his first transformation into Kamen Rider Kaixa.
Mari, Takumi, and Keitaro begin looking for Mari’s schoolmate Masato Kusaka.
Yuji has decided not to attack humans. Kaido is still trying to figure out what he wants. Yuka is trying to figure out Kaido. Kaido decides to be human and date. He drags Yuka out on a practice date.
Takumi, Mari, and Keitaro find Masato. As he and Takumi have a fencing battle, Mari’s former schoolmates are attacked by an Orphenoch. They go to rescue them. Masato follows and transforms using the Kaixa belt. He defeats the Orphenochs.
After Masuda dies from using the Kaixa Gear, Mari, Takumi, and Keitaro begin looking for Mari's schoolmate Masato Kusaka. Kiba decides not to attack humans but Kaido is still trying to figure out what he wants. Mari finds Kusaka at fencing practice. Kaido decides to live as a human and takes Yuka out on a pretend date as practice for Mari. Kusaka and Takumi have a fencing battle as Mari's old schoolmates are attacked by Equisetum Orphenoch. Haruko is killed by the Crocodile Orphenoch. They go to rescue them, with Kusaka following and transforming into Kamen Rider Kaixa to defeat the Orphenochs.
- Takumi Inui (乾 巧 Inui Takumi): Kento Handa (半田 健人 Handa Kento)
- Mari Sonoda (園田 真理 Sonoda Mari): Yuria Haga (芳賀 優里亜 Haga Yuria)
- Keitaro Kikuchi (菊池 啓太郎 Kikuchi Keitarō): Ken Mizorogi (溝呂木 賢 Mizorogi Ken)
- Yuji Kiba (木場 勇治 Kiba Yūji): Masayuki Izumi (泉 政行 Izumi Masayuki)
- Yuka Osada (長田 結花 Osada Yuka): Yoshika Kato (加藤 美佳 Katō Yoshika)
- Naoya Kaido (海堂 直也 Kaidō Naoya): Mitsuru Karahashi (唐橋 充 Karahashi Mitsuru)
- Masato Kusaka (草加 雅人 Kusaka Masato): Kohei Murakami (村上 幸平 Murakami Kōhei)
- Rina Abe (阿部 里奈 Abe Rina): Rie Kasai (河西 りえ Kasai Rie)
- Kyosuke Tokumoto (徳本 恭輔 Tokumoto Kyōsuke): Shun Saeki (佐伯 俊 Saeki Shun)
- J (ジェイ Jei): Kenneth Duria (ケネス・ヅリア Kenesu Zuria)
- Itsuro Takuma (琢磨 逸郎 Takuma Itsurō): Jun Yamasaki (山崎 潤 Yamasaki Jun)
- Saeko Kageyama (影山 冴子 Kageyama Saeko): Waka (和香 Waka)
- Masuda (増田): Michihiro Yamanishi (山西 道広 Yamanishi Michihiro)
- Haruko Kamijo (上条 晴子 Kamijō Haruko): Hiroko Hayashi (林 裕子 Hayashi Hiroko)
- Mari Sonoda (Child): Aoi Yuki (悠木 碧 Yūki Aoi)
- Masato Kusaka (Child): Yusuke Ito (伊藤 祐介 Itō Yūsuke)
- Ichiro Kusaka (草加 一郎 Kusaka Ichirō): Makoto Wakabayashi (若林 誠 Wakabayashi Makoto)
- Office Clerk: Keiko Kono (河野 景子 Kōno Keiko)
- Student: Kusano Makoto (草野 誠 Makoto Kusano), Keiichi Aiba (饗場 圭一 Aiba Keiichi), Shiro Go (郷 志郎 Gō Shirō), Tomonori Sato (佐藤 智則 Satō Tomonori), Noriko Sakurai (桜井 典子 Sakurai Noriko)
- Gangs:Fumiya Touei (藤榮 史哉 Tōei Fumiya), Takeyuki Honda (本多 剛幸 Honda Takeyuki)
- As part of Super Hero Time, this episode aired alongside Bakuryuu Sentai Abaranger episode 10, Ep. 10: Abare Leaguer Bind.
Blu-ray Box 1 comes with 17 episodes.