Nothing out of the ordinary with 異常

Kanji Explanation: Difference and strangeness with 異

Yui, Sacchan, and Kotoha go on an early-morning patrol to check for any issues in their neighborhood. Because it’s so early, none of the shops are open yet, and the streets are empty.

さっちゃん:: 「朝(あさ)は平和(へいわ)だ」; “Morning is peaceful.”
結衣(ゆい):: 「朝(あさ)は平和(へいわ)だね」; “Morning is peaceful, isn't it?”
琴葉(ことは):: 「異常(いじょう)なし」; “No abnormalities.”; Literal: “No abnormality.”

Key Points

1異常 means abnormality

異 carries the idea of difference or strangeness; 常 is the normal state.
Together, 異常(いじょう) is something out of the ordinary.

2異常(いじょう)なし is a report-style phrase

It means “no abnormalities” or “nothing unusual”.
Kotoha says it like a patrol report, matching the girls’ mission.