まがきじゃありませんでした
真牡蠣じゃありませんでした
maga kija arimasendeshita

Noun
Desu Copula

The polite, past negative form of まがき

1. It wasn't a real oyster.; It wasn't genuine oyster.

Past/Perfective
Negative
Polite
Terminal Form
Usually Written in Kana