Sega NET MJ — Mahjong Plaza

Q: Is Sega NET MJ American Mah Jongg or solitaire?

No. The official hub calls it a SEGA-operated **ネットワーク対戦麻雀** service; Free mode, private rooms, and **MJ四麻ルール** describe live 対人 / 四人 table play. It is not an NMJL-card American product and not a tile-matching puzzle.

Q: Is it free?

Hub and store copy say play is **基本無料** / Free-mode online 対戦 is described as free; optional GOLD / iGOLD / xGOLD purchases and In-App Purchases exist for chips and extras. Exact free vs paid table limits change — confirm the live hub or store page.

Category: Home games · Japanese Riichi online
Also called: セガNET麻雀 MJ; SEGA NET Mahjong MJ; NET麻雀 MJ; MJモバイル
Last checked: 2026-09-10

What it is

Sega NET MJ (セガNET麻雀 MJ) is a first-party online multiplayer Japanese Riichi (Japanese mahjong) service from 株式会社セガ (SEGA CORPORATION). Official hub and store copy frame it as a ネットワーク対戦麻雀 / 本格対人麻雀 product — live table matches against other players on PC (native Windows client and PC browser), iPhone/iPad, and Android, with ranked/official modes, free matchmaking, private rooms, spectating tools, and a dan-rank system. It is not American Mah Jongg, not Chinese Official / MCR as the primary product, and not solitaire tile-matching.

Who it’s for

Players who want competitive or casual live Riichi at home on PC or mobile, labeled clearly as Japanese online 対戦 / 対人 mahjong rather than an NMJL-card American table or a Shanghai-style puzzle.

Why it’s listed

Plaza needs a citeable Home-games slot for SEGA’s first-party home NET MJ client that is not already on disk (not Tenhou, RonRon / 龍龍, Mahjong Soul, Riichi City, Mahjong 4 Friends, Mahjong Time, or other home-game files).

Official hub (https://sega-mj.com/) loaded on 2026-09-10. Page title セガNET麻雀 MJ | SEGA; meta description: 『セガNET麻雀 MJ』はセガが運営するネットワーク対戦麻雀ゲームです。PCとiPhoneとAndroidで、いつでもどこでも手軽に対局可能！登録不要ですぐに遊べます。 Body pickup frames arcade MJ brought to home play, 全国イベント、段位システム, and PCとモバイルが１つのIDでプレイ. Hub download / store links include Windows installer (MJ_Setup.exe), PC browser play, App Store, and Google Play.
Free matchmaking guide (https://sega-mj.com/players/gameguide/manual/mode/free_match/): 無料で気軽に全国のプレイヤーとオンライン対戦が楽しめます; ranking table lists 東風 places 1位–4位 (four-player) plus 三麻. Private-room guide (https://sega-mj.com/players/gameguide/manual/mode/private_game/): 友人同士でのオンライン対戦やCPUを含めた対戦などが無料でプレイできます.
Official players-site news (https://pl.sega-mj.com/official_view/page?news_id=8917) dated 2026/3/5: 「フリー対戦四麻半荘」正式追加 — confirms ongoing first-party 四麻 (four-player) Free-mode tables in 2026.
Official rules (https://sega-mj.com/players/gameguide/manual/rule/rule_a/): MJ四麻ルール — アリアリ (食いタン / 後付け), 一発 / 裏ドラ / 赤ドラ, 25000点持ちの30000点返し, 順位ウマ for seats 1位–4位. Separate MJ三麻ルール also exists. Confirms real multiplayer table rules, not tile-matching.
Google Play セガNET麻雀 MJ (https://play.google.com/store/apps/details?id=jp.co.sega.am2.MJMobile): developer SEGA CORPORATION; About copy: 基本無料 / 本格対人麻雀 / compete online with players nationwide; Play developer address printed 1-1-1, NISHISHINAGAWA … SHINAGAWA-KU, 東京都 141-0033 Japan. Listing showed Updated on Sep 4, 2026 on this check.
App Store セガNET麻雀 MJ (https://apps.apple.com/jp/app/id666206963): seller SEGA CORPORATION; Free · In-App Purchases; same 本格対人麻雀 / スマホ・PC framing.
First-party 特商法 / 資金決済法 page (https://sega-mj.com/players/support/asct/): 名称 株式会社セガ; 住所 〒141-0033 東京都品川区西品川一丁目１番１号住友不動産大崎ガーデンタワー; 代表者 内海州史. Prepaid currency names include GOLD / iGOLD / xGOLD for PC, Android, and iOS clients.

No NMJL card, Charleston, or American scoring appears on those official pages. Table play is framed as online 対戦 / 対人 against other people — not a tile-matching solitaire board.

Official URL

Hub: https://sega-mj.com/

Players / play guide: https://sega-mj.com/players/gameguide/manual/

Free matchmaking: https://sega-mj.com/players/gameguide/manual/mode/free_match/

Private rooms: https://sega-mj.com/players/gameguide/manual/mode/private_game/

MJ四麻ルール: https://sega-mj.com/players/gameguide/manual/rule/rule_a/

Google Play: https://play.google.com/store/apps/details?id=jp.co.sega.am2.MJMobile

App Store: https://apps.apple.com/jp/app/id666206963

Shop / legal (特商法・資金決済法): https://sega-mj.com/players/support/asct/

Location

Play is online (Windows PC client, PC browser, iOS, Android). Operator: 株式会社セガ / SEGA CORPORATION. Address printed on the 特商法 page and Play developer field: Sumitomo Fudosan Osaki Garden Tower, Nishishinagawa 1-1-1, Shinagawa-ku, Tokyo 141-0033, Japan. Hub also links a separate arcade MJ product line; this listing is for the home NET / mobile / PC service.

Notes

Japanese Riichi / Japanese mahjong only as the listed rule family. Do not blur this into American Mah Jongg or Chinese Competition Rules.
Online 対戦 multiplayer tables — Free mode and official modes feature 四麻 (four-player; 東風 / 半荘) plus 三麻; private rooms support friend 対戦 — not solitaire tile-matching.
Hub, Free / private guides, MJ四麻ルール, Play, App Store, and 特商法 pages loaded on 2026-09-10.
UI is primarily Japanese (client language options may include English for in-match text — confirm the live client yourself).
Related arcade cabinets exist under the same MJ brand; this Plaza slot is the at-home NET / mobile / PC multiplayer product.
Not affiliated with Mahjong Plaza.

FAQ

Q: Is Sega NET MJ American Mah Jongg or solitaire?
A: No. The official hub calls it a SEGA-operated ネットワーク対戦麻雀 service; Free mode, private rooms, and MJ四麻ルール describe live 対人 / 四人 table play. It is not an NMJL-card American product and not a tile-matching puzzle.

Q: Where can I play?
A: Official hub https://sega-mj.com/ links Windows PC download, PC browser play, Google Play, and the App Store (SEGA CORPORATION). Players-site guides cover Free matchmaking and private rooms.

Q: Is it free?
A: Hub and store copy say play is 基本無料 / Free-mode online 対戦 is described as free; optional GOLD / iGOLD / xGOLD purchases and In-App Purchases exist for chips and extras. Exact free vs paid table limits change — confirm the live hub or store page.