いっし
one child; only child; one of several children (esp. the son and heir); one stone
Noun
一子いっしちゃんは同おなじ穴あなのムジナか、同輩どうはいの親したしみを込こめた笑えみを俺おれに向むける。
I guess Ichiko is a fellow rule-breaker, she's sending me a smile filled with affection for a comrade.