| National Diet | Founded | 29 November 1890 (135 years, 267 days) | 1.00 | infobox |
| National Diet | House of Councillors political groups | .mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;… | 1.00 | infobox |
| National Diet | House of Councillors political groups | JIP (19) | 1.00 | infobox |
| National Diet | House of Councillors political groups | CDP (40)[a] | 1.00 | infobox |
| National Diet | House of Councillors political groups | DPFP (25) | 1.00 | infobox |
| National Diet | House of Councillors political groups | Kōmeitō (21) | 1.00 | infobox |
| National Diet | House of Councillors political groups | Sanseitō (15) | 1.00 | infobox |
| National Diet | House of Councillors political groups | JCP (7) | 1.00 | infobox |
| National Diet | House of Councillors political groups | Reiwa (5) | 1.00 | infobox |
| National Diet | House of Councillors political groups | CPJ (2) | 1.00 | infobox |
| National Diet | House of Councillors political groups | Okinawa Whirlwind (2)[b] | 1.00 | infobox |
| National Diet | House of Councillors political groups | Team Mirai (2) [c] | 1.00 | infobox |
| National Diet | House of Councillors political groups | SDP (2) | 1.00 | infobox |
| National Diet | House of Councillors political groups | LDP (1/Speaker) | 1.00 | infobox |
| National Diet | House of Councillors political groups | CDP (1/Vice Speaker) | 1.00 | infobox |
| National Diet | House of Councillors political groups | Independent (4) | 1.00 | infobox |
| National Diet | House of Councillors political groups | Vacant (1) | 1.00 | infobox |
| National Diet | House of Councillors voting system | Parallel voting: Single non-transferable vote (148 seats) Party-list proportional representation (100 seats) Staggered elections | 1.00 | infobox |
| National Diet | House of Representatives political groups | LDP (316)[d] | 1.00 | infobox |
| National Diet | House of Representatives political groups | JIP (36) | 1.00 | infobox |
| National Diet | House of Representatives political groups | CRA (48) | 1.00 | infobox |
| National Diet | House of Representatives political groups | DPFP (28) | 1.00 | infobox |
| National Diet | House of Representatives political groups | Sanseitō (15) | 1.00 | infobox |
| National Diet | House of Representatives political groups | Team Mirai (11) | 1.00 | infobox |
| National Diet | House of Representatives political groups | JCP (4) | 1.00 | infobox |
| National Diet | House of Representatives political groups | Independent (7)[e] | 1.00 | infobox |
| National Diet | House of Representatives voting system | Parallel voting: First-past-the-post voting (289 seats) Party-list proportional representation (176 seats) | 1.00 | infobox |
| National Diet | Houses | House of Councillors (upper house) | 1.00 | infobox |
| National Diet | Houses | House of Representatives (lower house) | 1.00 | infobox |
| National Diet | Last House of Councillors election | 20 July 2025 | 1.00 | infobox |
