Historical clue formulations

• World's second-most-populous island — 2026-08-28
• Osaka's island — 2026-05-30
• Where Tokyo is — 2019-08-25
• Main part of Japan — 2013-01-15
• Island south of Tsugaru Strait — 2011-11-27
• Island whose name means, literally, "main land" — 2011-05-13