ましちゃう
togisumashichau

Godan Verb (su)
Godan Verb (u)

The completive aspect (contracted form) - indicates completion or regret of 研ぎ澄ます

1. Sharpening (up) completely; Sharpening (to a point); Polishing (to perfection); Becoming keenly aware; Regretting (sharply)

Completed Action
Colloquial