Kou Misaki

Machine learning researcher at Sakana AI, Tokyo

Portrait of Kou Misaki

I research methods that make large language models perform better by spending more compute at inference time, an approach known as inference-time scaling.

First-author papers
ICML 2026, ICLR 2026, NeurIPS 2025 (Spotlight)
Before Sakana AI
Apple (Japanese Siri), Recruit
PhD
Theoretical Physics, The University of Tokyo

Selected Publications

  1. ICML 2026

    UnMaskFork: Test-Time Scaling for Masked Diffusion via Deterministic Action Branching

    Kou Misaki, Takuya Akiba

    • inference-time scaling
    • diffusion language models
    • MCTS

    We propose an inference-time scaling method for masked diffusion language models in which multiple models collaborate during unmasking, with Monte Carlo tree search choosing among their deterministic unmasking steps. It outperforms existing inference-time scaling methods on coding benchmarks and scales well on math reasoning.

  2. ICLR 2026

    String Seed of Thought: Prompting LLMs for Distribution-Faithful and Diverse Generation

    Kou Misaki, Takuya Akiba

    • prompting
    • output diversity
    • probabilistic instruction following

    LLMs often fail to make choices according to given probabilities: asked to flip a fair coin, they don't return heads and tails equally often. We show that prompting alone largely fixes this. Asking the model to first write a random string and then derive its answer from it brings its choices close to the target probabilities and makes open-ended answers more diverse.

  3. NeurIPS 2025 Spotlight

    Wider or Deeper? Scaling LLM Inference-Time Compute with Adaptive Branching Tree Search

    Yuichi Inoue*, Kou Misaki*, Yuki Imajuku, So Kuroki, Taishi Nakamura, Takuya Akiba

    * Equal contribution

    • inference-time scaling
    • MCTS
    • Bayesian modeling

    We propose AB-MCTS, an inference-time scaling method for LLMs that extends Monte Carlo tree search: using Bayesian reward modeling, it decides at each step whether to sample a new answer or refine an existing one. Across a range of coding and engineering tasks, it consistently outperforms repeated sampling and standard MCTS. As part of this work, I developed TreeQuest, the accompanying open-source library.

Other Publications

  1. ALIFE 2026

    Shachi: A Modular, Controllable Framework for LLM-Based Agent-Based Modeling of Emergent Collective Behavior

    So Kuroki, Yingtao Tian, Kou Misaki, Takashi Ikegami, Takuya Akiba, Yujin Tang

  2. ICLR 2025 Spotlight

    TAID: Temporally Adaptive Interpolated Distillation for Efficient Knowledge Transfer in Language Models

    Makoto Shing, Kou Misaki, Han Bao, Sho Yokoi, Takuya Akiba

Full list on Google Scholar.