GetSingleton() requires that exactly one entity exists that matches this query, but there are 0.

[last wave]

I posted this question on the Unity forum 3 days ago and received some invalid replies because my sample code was too simple, leading to misunderstandings.
I've edited the code and added some images to my question, and I think I can get more efficient help if I ask for help here too.
https://forum.unity.com/threads/getsingleton-requires-that-exactly-one-entity-exists-that-matches-this-query-but-there-are-0.1472070/

[scarlet helm]

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[novel spear]

Just add in OnCreate RequierForUpdate<EnemyOne>

Subscenep load async