I caught two of these winged queen ants today. At 15mm long, this is the biggest species of ant I’ve ever found. It’s called kuro-oo-ari (black-big-ant) and is common throughout Japan.

Japanese ant database: http://ant.edb.miyakyo-u.ac.jp/E/Taxo/F80902.html

Camponotus japonicusCamponotus japonicusCamponotus japonicus

Hymenoptera: Formicidae (ants)
Camponotus japonicus (kuro-ooari)