Voiced by: Tatsuhisa Suzuki
Koutarou's Best Friend.
- Big Brother Instinct: Towards his little sister Kotori. This waffles between My Sister Is Off-Limits! and worrying that she is to shy. He wants Koutarou to "take responsibility" of her as a result.
- The Charmer: Known for his good looks and is the usual romantic lead for the drama club.
- Chick Magnet: He's known (infamously) as a ladykiller, attracting more ladies than Koutarou. Though unfortunately for him, what he wants is quality (which his best friend gets), not quantity.
- In-Series Nickname: "Makenzie" (Matsudaira Kenji)
- Kid-anova: For which Koutarou naturally gives him lots of grief. The relationships don't usually last long.
- Locked Out of the Loop: He has no idea what goes on at Corona House and especially his best friend's life.
- Looking for Love in All the Wrong Places: The women he is most attracted to are all attracted to Koutarou.
- Muggle Best Friend: He's the only completely normal person in Koutarou's life.
- Vitriolic Best Buds: Not quite as loudly as Theia and Koutarou but fairly constant.
The Cosplay Club
The cosplay club that Yurika and Maki are part of.
The Unpopular Boys AllianceA group consisting of 8 boys (with Koutarou as the leader) that are not popular with the ladies.
A girl that appears in Volume 23 and a love rival for the invaders (for them anyway).
Yuuichirou Satomi & Takami SatomiKoutarou's father and (deceased) mother.
Sanae's mother and Nana's former partner.
- Sacred Bow and Arrows: Her weapon of choice.
Voiced by: Atsushi Tamaru (Red), Tooru Sakurai (Blue), Rena Maeda (Pink), Ayumu Murase (Green), Kouji Seki (Yellow), Yoku Shioya (Dr. Roppongi)
A Sentai unit created by the Japanese government to battle evil-dwellers who lurk Beneath the Earth, consisting of Kenichi (Red Shine), Hayato (Blue Shine), Megumi (Pink Shine), Kotarou (Green Shine), Daisaku (Yellow Shine) and their sponsor Dr. Roppongi. Their technology was actually leaked to them by the People of the Earth's conservative faction in order to put pressure on those who wish to invade the surface.
- A Day in the Limelight: An off-duty Daisaku appears in book 27 to compete against the protagonists in an eating contest. Koutarou is disappointed that it couldn't be the The Leader who challenged them instead.
- Color-Coded Characters: Parodied in their first appearance, where due to budget constraints the team consists of five "Red Shines". Koutarou (playing the villain of the stage show they'd mistakenly interrupted) is actually offended that they'd put so little effort into the whole hero thing.
- Five-Man Band: A deliberately cliché example.
- The Leader: Kenichi (Red Shine), a Hot-Blooded man who fights with a Sword and Gun to be adaptable to all situations.
- The Lancer: Hayato (Blue Shine), a Cold Sniper and the team's staff officer.
- The Smart Guy: Kotarou (Green Shine), the Demolitions Expert with a talent for figuring out enemy positions.
- The Big Guy: Daisaku (Yellow Shine), a man with Stout Strength and great skill at martial arts.
- The Chick: Megumi (Pink Shine), a woman with an automatic rifle which she uses to pin down enemies, as well as a comedically over-the-top crush on "Baron Demon".
- Hero Worship: Towards "Baron Demon" (Koutarou) for helping them kick their team into shape, to the point of considering him an honorary Sixth Ranger. This only increases when they see him charge into battle with his own team of mysterious warriors behind him.
- Martial Arts Headband: Kenichi is usually seen wearing one, reflecting his Hot-Blooded status.
- One Steve Limit: Green Shine's real name is Kotarou, extremely similar to that of the protagonist Koutarou.
- Scarf Of Asskicking: In their civilian outfits, each of the team wear one in their signature colour.
- Super Strength: Their spiritual-power suits quintuple the wearer's strength.
- Teeth-Clenched Teamwork: Surprisingly averted when the Sun Rangers receive contact from members of the People of the Earth, who explain that they're from a conservative faction which doesn't wish to invade the surface. Not only do the Sun Rangers accept them as allies almost instantly, they're actually relieved that the People of the Earth can be reasoned with and they won't have to fight a war of extermination.
- Took a Level in Badass: While first introduced as incompetent (to the point where their rolecall consists of the the entire team introducing themselves as "Red Shine"), by their second appearance they've undergone serious training to improve their teamwork and fighting ability. By their third appearance Koutarou claims that each member is likely stronger than he is.
- Trademark Favorite Food: Fitting the Sentai Yellow cliché, Daisaku loves eating curry.
Hachi + ???
- Cut Lex Luthor a Check: When the hunters explain that they planned to sell Sanae for 300 million yen, Kiriha cuts off any future threat from the duo by simply buying Sanae herself at that price (on the condition that they share all the information they'd gathered on her). Book 11 reveals that this is when Kiriha learned of the living Sanae's existence, and employed the hunters to keep monitoring her.
- Depleted Phlebotinum Shells: Their tools include bug nets which can snare ghosts, and smoke bombs which block their Aura Vision (described as being created from the branches of sacred trees). Most of them appear to be things they've purchased from niche companies rather than created themselves.
- Fat and Skinny: The younger brother (Hachi) is short and fat, the unnamed older brother is tall and skinny.
- No Name Given: The older brother is only ever addressed as aniki ("big bro").
- Sibling Team: A pair of brothers who run their business together.
- Who You Gonna Call?: Describe themselves as professional bounty hunters who specialise in capturing ghosts.
- Bishōnen Line: When her giant form briefly absorbs Sanae it becomes opaque and gains a more human shape.
- Fusion Dance: Can fuse with other evil spirits to grow into a larger monstrous form.
- Mook Promotion: Introduced as one of the ghost hunters' minions, but hijacks their plans by trying to absorb Sanae.
- No Name Given: It's unknown what name she had when alive.
- Not Quite Dead: After her apparent destruction she manages to cling on to existence through The Power of Hate, returning in book 11 to attack Sanae a second time.
Alexei BelachevA spy from the struggling Melgaard Republic who appears in book 28. After Forthorthian ambassadors make First Contact with Earth, he is among the legions of agents scrambling to get their hands on alien technology. When he hears reports of a School Play with a land named "Forthorthe" as its setting, he travels to Kisshouharukaze to investigate its author Theiamillis.
- Hero Antagonist: Has no evil intentions behind his actions, simply wanting a better life for his wife and son. The protagonists sympathise greatly with his situation, but don't want to risk leaking Forthorthian weapon technology or the existence of the (currently vulnerable) People of the Earth.
- One-Winged Angel: After the protagonists convince him he was on a wild goose chase, his despair somehow summons the Whirlpool of Chaos, causing him to first enlarge in size, then transform into a humanoid dragon as he is influenced by the remnants of Vandarion's mind.