As the Japanese proverb "let your opponent slash your skin to cut off his flesh, and let him cut your bone to break his bone marrow" (you should be prepared to sacrifice your own body so that you can defeat your opponent) describes, the idea that the fencer himself or herself should win and survive is always behind the concept of aiuchi in swordsmanship schools.
皮を斬らせて肉を断つ～骨を斬らせて髄を断つとあるように、剣術流派における相打ちの概念とは、自分が勝って生き残る事が前提である。