Rei Yokoyamada is a 16 year old high school student who wants to follow in his movie producer father's footsteps by making a movie to submit to a film festival. After a classmate asked to take the role of the female lead bows out, he wanders the neighborhood and sees posters announcing that Papico (real name "Chiho Johansson"), a buxom AV actress that Rei is a fan of, lives in the area. Events soon transpire that cause Rei and Chiho to meet in person. The two quickly become friends and start chatting online.
Then Chiho finds a middle-aged man in his underwear bleeding on the sidewalk. When she tries to help, the man turns into a doll, leaving her with a DVD and a mysterious device implanted into her wrist that allows her to turn into a giant.
Gigant is a manga by Hiroya Oku (of Gantz and Inuyashiki fame). It is printed in the magazine "Big Comic Superior" starting in 2018 and combines a slice-of-life realism to the characters with the science-fiction weirdness that the mangaka is known for.
This manga provides examples of:
- Age-Gap Romance: Rei is 16 while Chiho is in her twenties, which is something that concerns her when they start dating.
- A Date with Rosie Palms: The first we see of Papico/Chiho is when Rei rubs one out to one of her videos.
- Behemoth Battle: Between the giant Chiho and the God of Destruction.
- Bland-Name Product: Rei has a lot of merch from movies and western comics, though the names and designs are tweaked just a little.
- But Not Too Foreign: Chiho Johansson, born from a Japanese mother and a Swedish father.
- Chivalrous Pervert: Rei clearly enjoys "Papico's" videos in the manner which they're intended for, but his reaction to seeing posters Slut-Shaming her posted around the neighborhood is to tear them down soon after because he doesn't think she should be bothered like that.
- Clingy MacGuffin: The mysterious device that allows Chiho to grow seems to be permanently glued to her wrist, and no matter what she tried, it didn't come off.
- Cover Innocent Eyes and Ears: A mother covers her kid's eyes as a giant naked Chiho passes over them.
- Disappeared Dad: Chiho's father is dead, leaving her as the family's main earner.
- Domestic Abuse: Played painfully straight when Chiho's boyfriend smacks her in a jealous fit after he sees how much she and Rei have been texting each other, then sobbingly apologizes after the two of them fight only to go right back to being a selfish jerkass the next times he's seen.
- Fiery Redhead: Though she's generally a nice person who quietly shoulders the crap in her life, if someone hits Chiho then she will hit back.
- Gainaxing: Suggested on chapter 18 as a giant Chiho is running through the city, with Motion Blur applied to her breasts.
- Giant Foot of Stomping: The God of Destruction is about to crush Rei when it is knocked away by Chiho doing a Dynamic Entry.
- Giant Woman: The wrist device at first makes Chiho about 3 meters tall. But when she thinks Rei has been hurt during the God of Destruction's attack, something triggers the device to make her grow big enough to fight the God (who is stated to be 240m).
- Internal Reveal: In chapter 7, Chiho shows Rei her size shifter ability in person, revealing to him that both her latest AV and the doll man's video were very real.
- Lazy Bum: Ryuuji, Chiho's slacker boyfriend, spends most of his time either playing video games or at the pachinko parlor. Similarly, the rest of her family seem to be relying on the money she makes from AVs to support their lifestyle.
- Mundane Utility: The first two people that Chiho's new size-changing ability are revealed to are her boyfriend and her boss. Both of them immediately say that she should make giantess porn.
- Nice Guy: Rei is generally a shy and considerate person. It's what draws Chiho to befriend him so easily when they first meet.
- Oh, Crap!: Rei's reaction upon seeing that the next phenomenon to be brought to life by the ETE site is the arrival of a "God of Destruction" that will wipe out most of Tokyo's population.
- On the Rebound: Invoked and downplayed. After Ryuuji runs out on Chiho, Rei's friend suggests that Rei should take advantage of this trope. While he does ask her out soon after, his feelings are sincere and she doesn't just jump into a relationship because she feels lonely after her break-up.
- Rain of Something Unusual: Early on, there's a rain of excrement. This is the first obvious act caused by a website that makes unusual phenomena occur.
- Ridiculously Cute Critter: Mochi, Chiho's pet corgi.
- Rose-Haired Sweetie: Chiho, for the most part.
- Scenery Censor: Used to hide Chiho's vagina when she's naked.
- Shapeshifting Excludes Clothing: Every time Chiho grows, her clothes rip off, leaving her naked.
- Size Shifter: The device in Chiho's wrist can be used to increase her size or return to normal.
- Slut-Shaming: Chiho ends up on the receiving end of it thanks to her line of work, even from her family who rely on the income she brings in. The whole meeting between her and Rei is triggered by a series of posters someone put up saying "The AV actress Papico is living on this street. Please let us do you."
- Time Travel: The doll man came from the future to stop "A's revolt". After seeing this on the video Chiho was given, Rei compares it to the plot of The Terminator.