Striped Eel Catfish (Plotosus japonicus) ゴンズイ
Juvenile Striped Eel Catfish form dense schools that move around like a dark blob. They also have venomous spines so best not to touch. There is also a Striped Eel Catfish (Plotosus ineatus) ミナミゴンズイ which lacks the yellow around the mouth. Gozashirahama