背黒 せぐろ海蛇 うみへびじゃありませんでした
seguro umihebijārimasendeshita

Noun
Desu Copula

The polite, past negative form of 背黒海蛇

1. Was not a black sea snake.; Was not someone with a dark heart/background.

Past/Perfective
Negative
Polite
Terminal Form