Top line says: "Type 3 Fighter Aircraft [Hien]" Version 1 Second Variant (Hien apparently translates as "Flying Swallow" )
Bottom line says: "244th Aviation Group, Captain Ikuno's aircraft" (I see the unit translated elsewhere as "244th Fighter Group).
Wiki has: Ki-61-I-Otsu Second production fighter variant: Tailwheel retraction mechanism was unreliable, the aircraft was modified accordingly. Two 12.7 mm (.50 in) Ho-103 machine guns replaced the wing 7.7 mm (.303 in) machine guns.
and for the unit: reorganised from 144th Sentai Ki-27, Ki-61, Ki-100 Okinawa, Formosa End of war (Yokaichi, Shiga Prefecture) Nine Bukosho recipients. Major Teruhiko Kobayashi JAAF's youngest Sentai commander. Also had an air-to-air B-29 ramming unit. Sentai claimed 73 B-29s shot down plus 92 damaged. Most famous of the Home Defence Sentais. Captain Nagao Shirai considered the ranking ace of 244 Sentai and possibly leading B-29 "killer" of JAAF (11 B-29s plus two F6Fs destroyed, six other aircraft damaged using Ki-61 and Ki-100. Captain Chuichi Ichikawa nine B-29s plus one F6F destroyed, six B-29s damaged. Major Teruhiko Kobayashi, three B-29s plus two F6Fs destroyed.
