|This article is about a/an ranger in Choudenshi Bioman.|
- ―Yellow4's roll call[src]
Jun Yabuki (矢吹 ジュン Yabuki Jun) became the second Yellow4 (2代目イエローフォー Nidaime Iero Fo) of the Biomen. She is an Olympic archer, who after watching the Bioman in action, tries to join them but is initially refused, even though Mika Koizumi had just died.
The others were looking for another descendant of the original five who were bombarded with the Bio Particles. However, Jun proves her courage, and it was also a pleasant surprise to discover that she has Bio Particles. It was thus with great joy that she was presented with a Bio Changer to become the new Yellow Four. She has to sacrifice her membership in the Japanese Olympic Archery Team, yet her skills become valuable to the Biomen.
In Episode 35 during their mission to find the mountain side where Mason and his squad are making explosions to collect magnetic rocks, she's the only person who takes down Shota Yamamori when she encounters him with her group for the second time. When her group takes to his home at Mt. Nekura, it reveals that Shota has feelings towards her which she remarks that he was admirable. When Shota was attacked by Mason, she as Yellow4 attempts to hit Mason with her Thunder Sword but dodges as Mason teleported. She was later relieved to see Shota was alive after surviving Mason's attack. In Episode 36, this deals their relationship. Jun tells him that he shouldn't get involved with their mission which Shota replies that he loves to take on danger places. Jun became dismayed towards him stating that he does not understand, he was a good person but he cannot join the team much to Shota's horrible shock and Jun angrily tells him not to argue and he has to go home as she leaves to join to her group causing Shota to be angrily desperate.
After Farrah reveals to the Biomen that Magne Warrior is Shota which Jun as Yellow4 was shocked as everyone got attacked by Magne Warrior's eye beam as they fall into the edge separately. As everyone reverted to their normal state as Shingo stated about people being exposed with magnetic energy. Jun realizes it was her fault for making Shota left behind as she set out alone to free him from being brainwashed leaving her group from behind.
As Jun confronts Shota as Magne Warrior, both had a fight as Magne Warrior manages to injure her left arm and Shirou and his group discovers Jun's feelings towards him and Jun notices that Shota's brainwashing was wearing off and she saw two bracelets that Shota was wearing as Magne Megas which is piloted by Farrah attempts to recharge his magnetic energy. Jun manages to destroy the bracelets with her two of her arrow shots from her bow and Shota was freed from brainwashing. After Shota was freed from brainwashing, he and Jun are fighting the mechaclones with their bow and arrows until Psygorn hits them with fireballs. After Red1 and the Biomen saved her, Shota decides to infiltrate the magnetic base alone as Jun gives her bow to him before transforming into Yellow4 to join the fray.
After Magne Megas was defeated, she and her group visit Shota's home at Mt. Nekura where Shota is seen in a white suit while fixing his home with his and Jun's names imprinted on it which he decides to marry Jun as her bride and living together as a married couple and making love as their honeymoon causing Jun to flee with his group as Shota watches as he gives a farewell to Jun.
Gaoranger vs. Super Sentai
Yellow4 is among the Sentai warriors seen in clips when Miku Imamura (MegaPink) lectured Sae Taiga (GaoWhite) about the past female Super Sentai warriors and their shared mastery of disguise and habit of changing their clothing in the blink of an eye, something that Sae had never done before.
Years later, Jun fought alongside not only her own team, but every single Sentai ranger in existence, against the Empire of Zangyack when it attacked the Earth in the Great Legend War. After fighting against hundreds of Gormin and their Zgormin commanders. Kaijou noticed the fleet moving towards them, he gathered all the Rangers together and gave them the order to sacrifice their powers to wipe out the first invasion's armada. The Yellow Four powers are later utilized by Luka Millfy via the Ranger Keys.
Farewell Space Pirates
After the Zangyack's final defeat, Marvelous returned the Ranger Keys to their original owners. Jun and her team have their powers again.
Super Hero Taisen
Jun, alongside her team, among the majority of the Super Sentai heroes, was caught up in the "Super Hero Taisen" incident which eventually resulted in the Super Sentai teams and Kamen Riders joining forces to defeat both Dai-Zangyack and Dai-Shocker.
Zyuohger vs. Ninninger
Yellow4 appeared with her team among the first 38 Super Sentai whom collectively empowered Wild Tousai Shuriken King in its fight against the titanic Gillmarda, granting the Ninningers and Zyuohgers the power to perform the Zyuoh Ninnin Super Sentai Burst which destroyed Gillmarda with the combined power of all 40 Super Sentai.
Super Sentai Strongest Battle
Jun joined the Super Sentai Strongest Battle as a member of Archer Team, but didn’t get to participate in the competition because her team was eliminated after losing the first round against Swordsman Team.
Stage Show appearances
In a stage show where the Biomen are seen fighting Neo Empire Gear and Bio Hunter Silva, Kamen Rider Stronger, Shaider, Kamen Machineman, DynaRed, DynaBlue, GoggleBlack, VulPanther, and DenziGreen arrive to assist the Biomen.
Video game appearances
- Mika Koizumi/Jun Yabuki/Yellow4: to be added
Super Sentai Battle Base
Yellow4 is among the vast pantheon of Rangers which are available in the mobile game Super Sentai Battle Base.
Super Sentai Legend Wars
Yellow4 appears with his team among all Sentai in the mobile game Super Sentai Legend Wars.
- Biojet 2 (shared with Green and Blue)
- Super Electronic Holography
- Strobe Flash
The Yellow4 Ranger Key (イエローフォーレンジャーキー Ierō Fō Renjā Kī) is Jun Yabuki's personal Ranger Key and what became of her powers after she along with the rest of the 34 Super Sentai sacrificed their powers to end the Great Legend War.
This key along with the majority of the Ranger Keys were collected by the Red Pirates and later used by the Gokaigers. The Yellow4 Ranger Key was mainly used by Luka Millfy (Gokai Yellow), who used it to fight as Yellow4.
- When the Gokaigers became the Biomen while fighting Kiaido.
The Bioman keys, along with all the Ranger Keys of the first 33 Super Sentai, were briefly taken by the Black Cross King and turned into Ranger puppets that were fought by the Gokaigers and the Goseigers. Splitting up, the puppet Yellow4 was defeated as part of a group of surviving Yellow warrior keys by Gokai Yellow and Super Gosei Yellow.
After Zangyack were finally defeated, the Gokaigers gave the Ranger Keys back to their rightful owners. Jun received her key and became Yellow4 once more.
- Jun shares her given name with Jun Kiyama (DenziYellow). Both Yellow Rangers shares two of the syllables in their respective Surnames Ki, which is the kanji for their Color and Ya.
- The first kanji in her surname (Ya) means "Arrow" which is a reference to her profession as an archer.
- She is the second Yellow Ranger Replacement, after Daigorou Kumano (Kirenger II) from Gorenger. Although unlike the Goranger replacement hers was permanent.
- Due to the fact she is a descendant of the original five people who were sprayed with Bio-Particles, it is believed that she is related to one of the other 5 Biomen. Due to her color scheme presumably she shares the same ancestor as her predecessor and the families branched out somewhere in the past, although assuming that Jun and Mika has the same ancestor, she was played by Mika's Actress Yuki Yajima. It can also be assumed that Jun and Mika may have at least one ancestor that was played by Jun's Actress Sumiko Tanaka.
- Unlike the other Biomen, when this series was dubbed into English in the Philippines, Jun retained her original Japanese name (or perhaps it was meant to be "June").
- She shares this trait with Riki Honoo as he also retained his Japanese name, though his name sounds like, or is possibly respelled into the English name of "Ricky".
- In the Philippine-English dub of the series, Jun was voiced by Dada Carlos; Jun was her first role as a voice actress.
- Mika Koizumi - the original Yellow4 that Jun temporarily replaced after her death.
- Aisha Campbell - First female Yellow Power Ranger replacement.
- Karone - First female replacement for a deceased Power Ranger.
- Trini Crystal - Power Rangers counterpart in Bio-Man. See comparison page.