A pretty clean room with 相当

Kanji Explanation: Mutuality and appearance with 相

Hiro lets Mao move into his sister’s bedroom, as Hina is living with relatives. After, he comes up with a list of rules that Mao needs to follow if she’s to keep living there.

基(ひろ):: 「…さて　片付(かたづ)け…」; “Now then, cleaning...”; 「できるのかな　おまえ…」; “I wonder if you can do it.”; 「俺(おれ)　陽菜(ひな)の部屋(へや)相当(そうとう)キレイにしてたんだぞ」; “I kept Hina's room pretty clean, you know.”; Literal: “I had made Hina's room considerably clean, you know.”

Key Points

1相当(そうとう) = “quite” as an adverb

Here 相当(そうとう) modifies キレイにしてた, so it means Hiro kept the room quite clean.
It is not “appropriate” or “equivalent” here; the scene is about degree.

2Casual sentence shape: 部屋(へや)(を)相当(そうとう)キレイにしてた

The object marker を is omitted in casual speech.
That means “I kept Hina’s room pretty clean”, not “Hina’s room became clean”.

3〜てた = casual 〜ていた

してた is the spoken contraction of していた.
It presents this as an ongoing state in the past: Hiro was keeping the room clean over time.

4んだぞ adds insistence

んだ gives an explanatory or assertive tone, and ぞ makes it sound rough and emphatic.
In context, Hiro is stressing his own track record to question whether Mao can manage the room.

A pretty clean room with 相当

Key Points

See Also