Yakyu24 (野球チームメーカー24, yakyu24.com) is an independent, unofficial baseball simulation about building a club through limited choices. It is not affiliated with other sites or tools whose names include “野球チームメーカー” (baseball team maker) or with their operators. This project contains no original-site code, copied site graphics, official club logos or player portraits.
Data scope
NPB: all 836 registered players of the 12 clubs in 2026 (batters/starters/relievers 404/155/277), from npb.jp rosters and first-team/farm stats as of 2026-09-16. MLB 718 (324/167/227) and KBO 102 (46/20/36) are selected official 2024 records, not complete rosters. NPB optionally adds 54 clearly fictional rookies.
Conversion method
Observed batting and pitching rates are compared with exposure-weighted sample means, centered on 70 and shrunk toward the mean for smaller samples. For NPB, farm stats are translated to first-team level using players who appeared at both levels, counted at half weight, and thin records shrink toward that farm (replacement) level. Each league has separate baselines; ratings do not compare leagues. Individual fielding is unassessed at 70. NPB OF and KBO IF/OF groups expand to game positions. NPB and KBO starters are inferred from at least three innings per appearance. NPB players use their real age from the roster birth date; MLB and KBO players start at a game age of 27. Ageing only applies after the reference season.
Simulation limitations
NPB:143 games/12 fictional clubs; MLB:162/30; KBO:144/10. Schedules are custom. MLB/KBO use a top-four custom playoff, not their official postseason. Errors, steals and detailed substitutions are not fully modeled. Win probabilities have not been calibrated to actual matches.
Before publication
No affiliation with real clubs, leagues or the original game creator is claimed. The operator must review data terms, names, trademarks and assets before launch. An unofficial disclaimer is not a grant of permission.