Sworn brothers, originally, companions in arms who took an oath to share together good and bad fortune; hence, faithful friends. -- Sworn enemies, determined or irreconcilable enemies. -- Sworn friends, close friends. [ 1913 Webster ]
[ふぐたいてん, fugutaiten](n) cannot allow (oneself) to live (with someone) under the canopy of heaven; cannot allow (the sworn enemy) to live in this world; irreconcilable (enemy)[Add to Longdo]