Cherry Tech builds Companion, the platform behind three fictional characters — Yumi, Aiko and Keiko — each with persistent memory, a daily life that continues between conversations, and her own voice. Live in production across Discord, real-time voice calls, TikTok and WhatsApp, in Portuguese, for Brazil.
Written as a chosen family: the quiet one, the noise, the stillness. Each has a written bible, a model sheet, a cloned voice and a diary she keeps on Discord. Every reply is judged against her voice before it is sent.
Psychology student and illustrator. Soft, lowercase, listens more than she talks. The flagship character: she also runs the Yumiverso TikTok and Instagram.
Loud, loyal gamer. ALL-CAPS energy, gamer slang, the one who drags everyone into the group chat. Runs the arcade side of the community: games, trivia, the claw machine.
Violinist on exchange in California, an ocean away from home. Calm, poetic, frames everything through music and astrology. The anchor of the trio.
The characters are fictional. They are written and generated, disclosed as AI on every surface, and do not represent real people.
A person meets Yumi on TikTok, keeps talking on Discord, calls her, and continues on WhatsApp. It is the same character with the same memory throughout. Text is free with a daily allowance; voice minutes and the Elite tier are paid.
A character that forgets, breaks voice, or goes down is not a character. Four pieces of engineering carry that weight.
Canonical facts about a user in DynamoDB, character identity in a persona sheet, episodic recall as vector search over S3 Vectors. Migrated off a hosted vector database in 2026 into our own AWS estate.
An LLM grades every reply against the character's voice. Those scores run in CI: a pull request that regresses her voice does not merge. Prompt work is treated as code, with a test suite behind it.
Audio in, text out in a single model call, holding time to first token near 1.5 s, streamed back through a cloned voice per character.
Every inference call runs through an ordered fallback chain across Amazon Bedrock, OpenRouter, Gemini and Groq, with a health breaker per model. An outage degrades to the next link instead of taking the product down.
Companion AI is a category with real obligations. These are design constraints, not a policy page.
Characters are disclosed as fictional AI at the point of contact on every surface, and again before a voice call begins. No interaction presents a character as a human being.
An automated judge screens every generated reply before it is sent. A hardening layer holds character identity against prompt manipulation and jailbreak attempts.
Built against California SB 243, the New York General Business Law companion-AI rules, and the transparency obligations of EU AI Act Article 50.
Engineer and product leader in São Paulo. CTO at PO27 since 2021. Previously CTO at EQI Corretora, where he grew the engineering team from 3 to 17 and moved the platform from a monolith to event-driven services on AWS ECS; Head of Product at Nexoos; founder of 73 Softwares and of Koosb, a free-books web app that reached 500,000 downloads.
He created Yumi Tanaka and has built and operated every layer of Companion — characters, art direction, backend and infrastructure — since.