MR stands for Mugen Racing. The Ninja JX engines were made in the OS Engines. These were made for Mugen Seiki and utilized the Ninja JX branding and were distributed by Mugen Seiki.
| Variant | |
|---|---|
| Type | Private |
| Parent Company | Mugen Seiki |
| Founded | 2006 |
| Divisions | Ninja JX |
| Headquarters | Funabashi, Chiba, Japan |
| Status | Active |
| Website | Click |