Not exactly like Saigo no Kizuna, but it shows the Japanese side of the Battle of Iwo Jima. Amazing actors, amazing story. Just a good movie directed by the amazing Clint Eastwood.
Both are about split brothers who must fight in enemy armies. Tae Guk Gi is more a typical action/war movie whereas Saigo no Kizuna is more a mixtype between war-drama and historical documentation because it tells the true story of two brothers who are alive nowadays.
Both are about underaged soldiers in Japans history. Saigo no Kizuna shows the Tekketsu Kinnoutai from Okinawa (second WW) and Byakkotai is a memorial for the young boys who fought in the Boshin war.