When the Cosmic Invading Grand Racing Crew, Hashiriyan intends to expand their territory with Earth being their next target to take over, five genius mechanics join forces with an alien machine named ...
Mira Shifuto's about to get married to a man she doesn't want to when she's suddenly whisked away by a deliveryman.
Ishiro still won't acknowledge Mira as a Boonboomger as the team has to deliver classified documents to a foreign ambassador.
Mira goes out on her first solo delivery while a clock-themed Hashiriyan tries to stop everything that moves.
After saving a child from getting hit by a truck, Mira is arrested by Officer Akuse and brought in for questioning by the International Space Agency.
Jou wants to become a Boonboomger, but Taiya rejects him, saying he doesn't have what it takes just yet.
Ishiro trails Jou, thinking his overly serious policeman persona might just be an act when a toilet-themed Hashiriyan starts forcing the truth out of people. Meanwhile, Taiya has to deal with a new foe.
Boonboom has fallen in love. Mira, as a delivery person, decides to take Boonboom to the person he loves. Boonboom falls in love with someone he never expected...!? Meanwhile, Taiya gives something to Genba.
Taiya reveals his real intentions to form the Boonboomgers, which is to participate in the "Big Bang Grand Prix", the biggest and most important race of the entire universe, while fighting the Hashiriyans was not in his original plans.
Taiya is seriously wounded after his fight with Mad Rex and Shirabe informs the team that the ISA decided to have the Boonboomgers disbanded and their equipment confiscated.
Genba has his first solo delivery job for the ISA. Worried about him, Mira decides to tag along, when the Sanseater attack the duo.
Taiya makes a special delivery to an old friend who inspired him to become a deliverer in the first place. Meanwhile, Cannonborg, another team captain arrives to assist the Sanseater in taking over Earth.
Taiya runs into a certain familiar Engine and takes on the job delivering him to his partner.
The Boonboomgers are afflicted by a mysterious phenomena that leaves them apathetic, while Genba approaches Itasha of the Sanseater with unknown intentions. Meanwhile, Cannonborg completes his secret weapon to counter Boonboomger Robo.
After Genba having successfully activated BoonBoom Safari, Ishiro and Mira pay a visit to an aquarium looking for inspirations to activate BoonBoom Marine, when the Sanseater return with a fixed-up Boonboom Killer Robo, eager for a rematch.
Jou finds a monster created by the Hashiryan who refuses to attack humans and befriends him, determined to protect his new friend from the enemy.
The Boonboomgers meet Sakito Homura, a mysterious man who possesses the same powers as them, able to transform into Bun Violet and whose intentions are unknown.
Sakito makes an offer to Taiya to join the team. Meanwhile, Sakito's partner Byun Diesel is an old acquaintance of Bundorio and wants to meet him again, but Boonboom refuses and the past between them is revealed.
At the Hashiriyan's request, Sakito starts trying to get rid of the Boonboomgers! Taiya asks him, "Why did you abandon the earth?" But...!? Will Sakito turn out to be a friend or foe!?
On Tanabata day, everyone is having fun, but only Boonboom remembers his bad past with the word "Milky Way". Then, a new Guruma appears, and Taiya is in the biggest trouble ever...!?
Mira's ex-boyfriend Norio unexpectedly reappears. And he is with the Hashiriyan for some reason!? Norio's "Wonderful Revenge Drama" begins in order to get his beloved Mira back from the Boonboomgers.
A series of unexplained fires have been burning down the town, and the people seem to be in trouble. Genba, who has become a "detective", deduces the cause.
Summer! Camping! Tent Grumer!? Tent Grumer interferes with children who are enjoying camping in the mountains. Then, Taiya and the others challenge the newly born "Boonboom Leon" to a battle!
A new monster has appeared on the ground! The Boonboomgers fight as usual...but for some reason, they decide to play a game of baseball. Boonboomger vs. Hashiriyan is a blazing hot battle, and "Boonboomger Robo 119", a Cho Bakugage Gattai robo, plays a big role in the battle!
The Boonboomgers came to the after-school daycare facility where Taiya used to attend. There, they learn about Taiya's first love. While they are having a good time talking about their sweet and sour memories, a new Grumer appears, and Taiya and Sakito are put to sleep by a mysterious attack...!?
Cannonborg is on his last legs, initiating a plan to destroy Earth from space.
Shirabe is to explain the Boonboomgers to the head of ISA. Meanwhile, Taiya and the others have to fight a familiar Grumer. What's more, something extraordinary happens...!? The 3rd LAP is about to begin.
A new powerful enemy has arrived, and Genba seems to have some history with him...
The team is distraught after Genba left and Jou decides to work even harder to make up for it.
Sakito and Byun help with Ichiro's spy job, while Taiya tells the others the story of how he and Ichiro met.
The Sanseater try to make Mad Rex recover his memories.
Mira works part-time on a curry restaurant she has loved since childhood. However, business is not as booming as it once was so the other Boonboomger decide to investigate.
Genba is defeated by Dissrace and rescued by Sakito when they run into a mysterious man on the railway tracks.
Genba has a heart-to-heart with someone he least expects. The Boonboomger use a new invention to transform into a powered-up form to confront Mad Rex.
The Sanseater blame the Boonboomger for Mad Rex's death as Taiya surprises the team with a new Boonboom Car, the Champion Carrier.
Taiya and the others are astonished upon discovering that Bundorio was once a Hashiriyan and worked with Wild Spindor.
Mira's childhood friend grows jealous of her as the Hashiriyan hatch a plan to send out two monsters at once.
Ichirou bumps into a spy with whom he used to work with, while the others are called into action to deal with a camera monster.
The Sanseater are greeted to the arrival of Wayway Yarucar, an elite member of the Yarucar race, as the Hashiriyan prepare for Spindor's arrival.
As ISA is making suspicious moves, Baisu Maimi, a co-worker of Shirabe, returns to Japan. Meanwhile, the Boonboomger are getting wiped clean.
A boy who admires Bun Blue appears and asks to become his apprentice. However, Ishirou does not want any part of it, leaving the situation to Bun Black instead.
Spindor is given the offer of the Earth's soccer league being part of his own Big Bang Soccer league, which Sakito and Genba take issue with.
Spindor is curious about Santa Claus and wants him kidnaped and brought before him.
Ishirou has been out of contact with Taiya for days when he suspiciously reappears, while at the same time, a space pirate appears with something important to give to the Boonboomger.
Distraught over having his fortune taken from him, Taiya heads out to find his mentor who is behind all this.
Taiya is devastated with Bundorio's apparent death and attempts to fix him up. Meanwhile, Dissrace returns and initiates a plan to turn the public opinion against the Boonboomgers but Sakito and Byun rise against him.
Society has turned on the Boonboomger, while Yaiyai Yarucar is turned into a Kurumaju with the power of all Kurumaju.
Mira is propositioned into a political marriage with Spindor as the team struggles with the fact that they may have lost.
The Boonboomger enter the final lap of their battle with the Hashiriyan.
