ShumpeiNagoshi

Probing the origin of the two-component structure of the broad-line region by reverberation mapping of an extremely variable quasar ↗

Monthly Notices of the Royal Astronomical Society (MNRAS 529, 393–408) / First author

Reverberation mapping of an extremely variable quasar revealed that its Hβ emission consists of two components — double-peaked when faint, single-peaked when bright — shedding light on the origin of the broad-line region's structure.

The relation between quasars' optical spectra and variability ↗

Publications of the Astronomical Society of Japan (PASJ 74, 1198–1208) / First author

Analyzing the spectra of ~10,000 quasars, showed that iron and oxygen emission-line strengths predict later brightness changes, and that line strength and luminosity vary while keeping a long-term correlation — a clue to how quasars gain mass over time.

Discovery of a new extreme changing-state quasar with 4 mag variation, SDSS J125809.31+351943.0 ↗

Publications of the Astronomical Society of Japan (PASJ 73, 122–131) / First author

Discovered a changing-state quasar that brightened by about 4 magnitudes in the optical between 1983 and 2015 — one of the largest known brightening events, and a starting point for the later variability studies.

Probing the origin of the broad-line region by reverberation mapping and multi-wavelength observations

European Astronomical Society Annual Meeting (EAS 2023) ・ Talk

Discovery of a new changing-look quasar 3C 332

Publications of the Astronomical Society of Japan (PASJ 73, 596–608) ・ Co-author

Spectroscopic and photometric observations of dwarf nova superoutbursts

Publications of the Astronomical Society of Japan (PASJ 73, 753–771) ・ Co-author

Spectroscopic identification of the transient TCP J20034647+1335125 as a dwarf nova

The Astronomer's Telegram 13947 ・ Co-author

A hidden ring around a supermassive black hole — 3D structure recovered from time-series data ↗

Kyoto University press release ・ Press release

Characteristic found in the brightness variation of quasars ↗

Kyoto University press release ・ Press release

Silver Prize

JCMA Challengers Live Osaka 2022

A close-up magic competition.

Mystic Prize

JCMA Challengers Live Osaka 2018

A close-up magic competition.

SelfPilot AI ↗

An AI program for solo owners and small businesses — build and publish a website in a weekend, and make AI a daily tool.

OTAtrip Guide ↗

Small-group walking tours led by local Kyoto guides — the hidden, inside Kyoto.

Message Coffee ↗

Gift coffee with a message — scan the QR code as you pour, and a message and photo rise with the steam.

ImmersiveNavi ↗

A service for immersive theater and ARG (alternate reality game) experiences.

HAZE coffee ↗

Specialty coffee with a built-in puzzle — an ARG paired with a cup, for a brew you remember.

NOROI ↗

"Your grudge, cursed on your behalf." An online curse-by-proxy — drive nails into a digital straw doll, a ritual offered as entertainment.

Seisokujo ↗

"The universe is watching you today, too." Not invented astrology — readings drawn from live space-weather measurements (solar flares, geomagnetic activity) and the actual sky at the moment you were born.

MAGI SYSTEM ↗

State your dilemma as a single proposition, and three AIs with distinct temperaments judge it independently, settling it by majority vote — each with its reasoning laid out.

Inori Message ↗

An iOS app for sharing wishes in the world of a Shinto shrine. Toss a coin to send a wish down the timeline, and strangers passing through send prayers back. No sign-up, free to use.

Magic Bar ENCORE ↗

An exploration-based web ARG — follow a magic bar's site, piece together the clues, and uncover the truth.

AIエージェント導入、最初の一歩 ↗

Kindle · in Japanese / July 2026

A short book for owners of small businesses on turning generative AI from a handy tool into a working system — choosing the first task to delegate, writing the brief, drawing the line on information security, and making it stick.

AI Agents: The First Step: For Small Businesses — How to Turn ChatGPT and Claude from a Handy Tool into a System That Works ↗

Kindle · in English / July 2026

The English edition of "AIエージェント導入、最初の一歩" — for owners of small businesses, the steps that turn ChatGPT and Claude from a handy tool into a system that works: choosing the first task to delegate, writing the brief, drawing the line on information security, and making it stick.

Don't Be That Tourist: Japanese Etiquette for Travelers, Explained by a Kyoto Tour Guide ↗

Kindle · in English / July 2026

An etiquette guide for visitors to Japan, written by a working Kyoto tour guide. Every custom is sorted into three temperatures — what causes a real problem, what people quietly notice, and what nobody minds at all — explained with reasons and 49 line illustrations.