そいつ
其奴 that person (guy, fellow) that (one)

そいとげる
添い遂げる to remain married for life

そいね
添い寝 sleeping together

そいぶし
添い臥し sleeping together

そいん
訴因 charge count 疎音 prolonged silence 素因 basic factor

そいんすう
素因数 prime factor