BitterSweet retention is all you need poster
Junseong and Sunghun with the BitterSweet retention poster

BitterSweet is built between San Francisco and Seoul by two longtime teammates. we first worked together as ML and data engineers at ScatterLab, then became the first team to win Asia's and Europe's largest hackathons in the same year.

we believe the AI era belongs to teams that can identify a real problem and solve it with a sharp idea. we're here for moonshots. we don't chase FOMO—we only care about high retention and user growth, the result of making products people genuinely love. that's the whole game.

we're now pivoting to our third product and looking for a problem worth spending the next decade on: something big, ambitious, and human-first—an experience people come to see as inevitable. we live in the future and build what's missing.

Junseong Kim · Co-Founder & CEO

linkedinjunseong@bittersweet.ai

  • 3 yrs ml scientist / 2 yrs ml engineer / 2 yrs ceo staff / total 7 yrs @ ScatterLab
  • built Luda Lee in 2018 — 2M MAU companion ai, before llms
  • built zeta in 2024 — 10m global users, 12 hr/week/WAU, in 2 years
  • super generalist — llm pretraining, inference optimization, finance, strategy, hiring
  • 2× national cs olympiad medalist

Sunghun Kim · Co-Founder & CTO

linkedinsunghun@bittersweet.ai

  • high-school dropout
  • grinded on cybersecurity (white hacking) for years
  • 7 yrs SWE since age 17
  • llm data flywheel at ScatterLab
  • core payments infrastructure at korea's top travel company