Only One Life (ひとつきりの命 Hitotsu kiri no Inochi) is the third episode of Ultraman Mebius.
Birdon has arrived. Can Mebius defeat this foe, one that previously killed an Ultraman?
On another night the woman in white (Bogar) appeared at an erupting volcano, GUYS discover an area on the side of the mountain to be withered and covered in sulfur, then the monster Birdon appears and attacks the area. Ultraman Mebius appears to stop him but, during the fight is stabbed by the monster's beak and injected with poison, leaving Mebius badly injured and Birdon to fly away towards the Pacific Ocean. The next day Teppei researches the fact of what the purpose of the Color Timer was and if an Ultraman can die. Later that day tracking shows that Birdon changed course and was heading back for the mainland. The Gun Phoenix was sent to intercept it but, even with METEOR proved futile and reached a coastal town. Mirai though weak and injured transformed into Ultraman Mebius though his Color Timer was still red. Teppei soon discovered to the rest of the team's horror that it represents that he is alive but, is not invincible. Mebius goes to fight Birdon and with the combined efforts of him and GUYS, they defeated the monster with the Mebium Shoot and the newest weapon the Capture Cube.
- Mirai Hibino (ヒビノ・ミライ Hibino Mirai), Ultraman Mebius (Voice) (ウルトラマンメビウス Urutoraman Mebiusu): Shunji Igarashi (五十嵐 隼士 Igarashi Shunji)
- Ryu Aihara (アイハラ・リュウ Aihara Ryū): Masaki Nishina (仁科 克基 Nishina Masaki)
- Marina Kazama (カザマ・マリナ Kazama Marina): Ai Saikawa (斉川 あい Saikawa Ai)
- George Ikaruga (イカルガ・ジョージ Ikaruga Jōji): Daisuke Watanabe (渡辺 大輔 Watanabe Daisuke)
- Konomi Amagai (アマガイ・コノミ Amagai Konomi): Misato Hirata (平田 弥里 Hirata Misato)
- Teppei Kuze (クゼ・テッペイ Kuze Teppei): Kenta Uchino (内野 謙太 Uchino Kenta)
- Shingo Sakomizu (サコミズ・シンゴ Sakomizu Shingo): Minoru Tanaka (田中 実 Tanaka Minoru)
- Aide Toriyama (トリヤマ補佐官 Toriyama Hosakan): Kenichi Ishii (石井 愃一 Ishii Kenichi)
- Secretary Aide Maru (マル補佐官秘書 Maru Hosakan Hisho): Yutaka Maido (まいど 豊 Maido Yutaka)
- Mystery Woman (謎の女 Nazo no Onna): Moeko Koyama (小山 萌子 Koyama Moeko)
- Ultraman Mebius Volume 1 features episodes 1-4.