Grammar Point
Godan verb with 'u' ending
v5u 
auxiliary verb
aux-v 
word usually written using kana alone
uk 
しまう

to do completely, to finish

after the -te form of a verb

Verb て form + しまう

The auxiliary verb しまう is used after the て form of a verb to indicate that an action has been completed or finished entirely. It emphasizes the finality of the action.

This construction is used with any verb in its て form to show that the action was carried out to the end.

I finished reading the book.

I ate all the cake.

I finished my homework.

Note

In casual speech, ～てしまう is often contracted to ～ちゃう and ～でしまう becomes ～じゃう. While this grammar point primarily indicates completion, it can also carry a secondary nuance of regret or accidentally doing something, though the core meaning remains the completion of the act.

Words: 
仕舞うしまう
終うしまう
了うしまう
蔵うしまう
Radicals of radicals