Abstract paintings by the toddler are on sale for 33,000 yen ($230) at her debut show at the hip gallery Decameron, tucked above a bar in the Kabukicho red-light district.
Thumbelina's vivid style is "babyish but mysteriously dexterous", gallery director -- and matchmaker of her parents -- Dan Isomura told AFP.
"I thought, 'wow, these are legit artworks'," Isomura said, describing his first impression of her free-form creations .
Colourful smudges adorn tatami mats and tables at the 21-month-old's suburban home, where her mother patiently helps twist open paint tubes and squeeze them onto paper.
"I can see this rhythm in her movements and patterns... she knows what she's doing," said the evacuee from Ukraine in her 20s, asking to remain anonymous for privacy reasons.
As a fellow artist focusing on Japanese calligraphy, she is "jealous" of her daughter's first solo exhibition, she joked, though of course "I'm happy, as a mum".
Once she thought her daughter might help her with work, but now "I'm her assistant".
- 'Like Cupid' -
After Russia invaded in 2022, Thumbelina's mother left Ukraine's eastern Donbas region -- her "very pathological, violent" homeland torn apart by war.
She found herself on a plane to Japan, having consulted a website helping Ukrainians find housing worldwide.
A chance seating beside contemporary artist Isomura, who had only boarded because of two delayed flights, changed her life.
Amazed to learn they were both artists, the pair kept in touch, and later, through Isomura's introduction, she met her future husband.
"Dan is our angel, you know, like Cupid," she said.
The couple then had Thumbelina -- not her real name -- whose paintings inspired 32-year-old Isomura.
At first he had assumed the toddler was "scribbling randomly, like she was playing in the mud".
But when he saw Thumbelina in action, "she seemed to signal each time she considered her drawing complete," prompting her mother to give her a fresh sheet.
The fact that Thumbelina sometimes demands a specific colour, develops shapes from paint droplets and finishes voluntarily suggests a will at work, he said.
"Some may say her mother's involvement means these are not Thumbelina's works," Isomura said.
But "for a baby, a mother is part of their body".
- Young creative mindset -
In any case, adult artists are not fully independent, Isomura argues, as they rarely break free of store-bought paints or conventional canvases.
"We operate under the illusion of solitary creation, while in fact we rely heavily on systems built by others," he said.
The exhibition, Isomura's first as director of Decameron, opened last month and runs until mid-May.
But most of the time it's on, from 8:00 pm until 5:00 am, Thumbelina will likely be fast asleep.
One recent night at the gallery, an admiring visitor said the paintings had an innocent charm.
"We instinctively try to draw skillfully" because "we've grown used to having our paintings evaluated by others", 45-year-old Yuri Kuroda told AFP.
"But it feels like she doesn't care at all about whether it's good or bad... It's a mindset we can never return to."
So would she pay $230 to take one home?
"I'm tempted," Kuroda chuckled.
tmo/kaf/rsc/tc
© Agence France-Presse
