The Winning Ball of Light (光のウイニングボール Hikari no Uiningu Bōru) is the fourth episode of Ultraman R/B.
Back in high school, Katsumi was a pitcher for his high school’s baseball team. The eldest of the Minato siblings gave up on his dreams when their mother disappeared so as to support his family. Katsumi shows off his burning fighting spirit in a retirement match for a local baseball team’s coach. Katsumi is injured during a battle with a monster and uses the coach’s words and skills as a pitcher to find renewed determination in his mission as Ultraman.
After the first win of the baseball season, the White Bears visit the Quattro M store for a team meeting. During the conversation, Kumashiro Matsuo (the coach) orders the team to practice the week after next, for the next match against The Johoku District team. However, he also states that he will be resigning as a coach and baseball player due to his health problems. Katsumi's determination to win the match becomes even stronger, as he doesn't want his coach to leave in shame. The team agrees on training hard for the match, though one member complains about the rival team being too strong.
Under the lead of Katsumi, the team trained harshly for the two weeks. But, the day before the game, Katsumi decided to train overnight. This brought up a fight between him and another teammate and Isami had to jump in to pull Katsumi out. Isami informs Katsumi that a kaiju has appeared near Mt. Muho and the two took off to investigate. Upon arrival, the brothers find a Red King lumbering across the terrain, so they transform into their Ultras to combat the monster.
Red King's strength proved to be too much for the brothers to handle and threw Rosso's Splash Bomb back at his shoulder. Red King defeated the Ultras and left the scene, so the brothers headed back to the city. Afterwards, Kumashiro finds Katsumi alone in the locker room of the stadium, and notices that his right shoulder is injured. Kumashiro treated the injury, and they begin talking about the monster that appeared at Mt. Moho. Kumashiro gives Katsumi three R/B Crystals (At the time where Kumashiro's ancestors found it during the Ayaka Comet incident, while telling that they had once dreamed about two giants of light) as a farewell gift.
The next day, the match with Team White Bears against the Johoku District starts. Makoto Aizen also shows up to cheer the two teams on, but mysteriously leaves claiming to use the restroom. Makoto walks into the forest and summons Red King to attack. In the late game, the White Bears were close to winning until suddenly, Katsumi notices Isami is gone. Kumashiro sees this and tells Katsumi to leave the match to accomplish his duty, and that he will play as the pitcher.
Katsumi arrives just in time to save Isami from Red King's choke and the two prepare to battle the beast once again. This time, the Ultras summoned their R/B Sluggers and rapidly slashed Red King's torso. Katsumi, decided to use the Zero Twin Slicer to finish the monster off, but his right shoulder (from the previous battle) prevented him from doing so. Blu, used his Aqua Jet Blast to heal the wound and the attack was finally performed. At the same time, Kumashiro threw the last pitch in the baseball game. In the aftermath of the battle, Makoto sends his AI D.R.L.N. to retrieve Red King's R/B Crystal.
Katsumi arrives on the baseball field and sees Kumashiro standing alone. Katsumi realizes that he's looking at the scoreboard and sees that his team had lost the match, thanks to one of the batters in Team Johoku District scoring a home run. He apologizes to his coach, but realizes that he truly doesn't care about winning or losing, saying that "it was a great game in the end" and thanks Katsumi for the sendoff.
In the final scene, Makoto is seen in a dim room, admiring his collection of R/B Crystals on the R/B Crystal Collection Case.
- Katsumi & Isami: R/B Crystal Navi!
- Isami: We are going to be studying R/B Crystals now Katsumi!
- Katsumi: Yeah. Today's crystal...is this!
- R/B Gyro: Ultraman Zero!
- Isami: Ultraman Zero is an Ultra Hero who specializes in intense fighting techniques. Equipping the R/B Slugger Rosso with the Zero Crystal activates the Zero Twin Slugger finishing move.
- Katsumi & Isami: Be sure to watch next time!
- Katsumi Minato (湊カツミ Minato Katsumi): Yuya Hirata (平田 雄也 Hirata Yuya)
- Isami Minato (湊イサミ Minato Isami): Ryosuke Koike (小池 亮介 Koike Ryōsuke)
- Asahi Minato (湊アサヒ Minato Asahi): Arisa Sonohara (其原 有沙 Sonohara Arisa)
- Ushio Minato (湊ウシオ Minato Ushio): Ginnojo Yamazaki (山崎 銀之丞 Yamazaki Ginnojō)
- Makoto Aizen (愛染マコト Aizen Makoto): Motoki Fukami (深水 元基 Fukami Motoki)
- Ultraman Rosso: Hideyoshi Iwata (岩田 栄慶 Iwata Hideyoshi)
- Ultraman Blu: Satoru Okabe (岡部 暁 Okabe Satoru)