How Japan's Music Charts Work — and How OSHIRABE Reads Them
Streaming, Billboard Japan, and a consumption signal found almost nowhere else in the world: karaoke. OSHIRABE fuses six fragmented sources into one weighted composite score. Here is how it works, and what each of the five charts shows.
オシラベ編集部
Japan has no single chart that tells you everything. Sales-based rankings, a composite chart that blends streaming and downloads, each streaming service's own ranking, and — uniquely — karaoke. Each reflects a different slice of the truth.
OSHIRABE exists to merge that fragmented picture into one.
Why Japan's charts are split
CDs were the center of Japanese music sales for decades, so sales-based charts carried enormous weight. Billboard Japan, meanwhile, uses a composite of streaming, downloads, radio and video, while each streaming platform publishes its own ranking. And then there is karaoke — what people choose to sing is a powerful signal of how deeply a song has taken root, yet almost no chart outside Japan captures it.
Look at any one source alone and you miss the full picture of what is actually a hit in Japan right now.
OSHIRABE's approach: a six-source weighted composite
OSHIRABE statistically combines six data sources into a single score.
- Apple Music (weight 0.30): one of Japan's largest streaming platforms. Updated daily.
- YouTube (0.20): uses the daily increase in plays (a daily delta), not cumulative totals.
- Billboard Japan (0.20): the industry-standard composite chart. Weekly.
- Karaoke, DAM + JOYSOUND (0.15): a consumption signal unique to Japan, absent from international charts.
- LINE MUSIC (0.10): streaming popular with younger listeners. Daily.
- Last.fm (0.05): a global listening signal used as a supplement. Daily delta.
Comparing sources fairly
Every source is normalized to rank points (1st = 100 pts, 100th = 1 pt: P = 101 − rank). That keeps very different sources comparable and prevents huge play counts or outliers from dominating.
Measuring momentum, not just totals
For YouTube and Last.fm, cumulative totals would let old songs sit on top forever, so OSHIRABE uses only the day-over-day increase (Δ = V(t) − V(t−1)) to catch what is rising now.
The five charts
- REAL HITS (overall): the flagship composite of all six sources.
- WAVE (rising): the day-over-day change in REAL HITS scores — pure new momentum.
- NEXT (new releases): recent releases only, with a per-artist cap so no single act dominates.
- COMEBACK (re-charting): detects songs over a year old surging again (TV, TikTok, film tie-ins).
- ARTIST 100: sums every charting song's score by artist across the REAL HITS top 100.
Transparency and rules
- The algorithm is public (methodology).
- It deliberately includes signals global charts ignore, like karaoke.
- Some sources are shown for reference only and are not scored (due to CD bias or terms-of-use limits).
- We never handle lyrics or audio.
A note for readers outside Japan: karaoke and "catalog" demand mean older songs often chart here in ways pure streaming charts never show. That is exactly what OSHIRABE is built to reveal.