かさ わせちゃう
kasaneawasechau

Ichidan Verb
Godan Verb (u)

The completive aspect (contracted form) - indicates completion or regret of 重ね合わせる

1. stacking/combining (and it happens); piling up (and it happens); layering (and it happens); doing something repeatedly (and it happens - with regret/emphasis)

Completed Action
Colloquial