diff --git a/Design:-Persistable-Context.md b/Design:-Persistable-Context.md
index 655f1dc..a9ffde0 100644
--- a/Design:-Persistable-Context.md
+++ b/Design:-Persistable-Context.md
@@ -576,6 +576,18 @@ The rules then become:
 3. no callback provided, store provided : for a `get` - throw an error. for a `set` - allow it
 4. callback provided, store provided : use specific store
 
+<details><summary><b>Discussion</b></summary>
+
+>HU: In rule 3, if an error occurs in asynchronous process in `set`, the error cannot be caught.  
+How do we handle it?
+>1. Ignore the error.  
+>2. Log the error.
+>3. Others  
+>  
+>I prefer 1. I think that the caller should decide whether to handle the error or not.
+  
+</details>
+
 I think that is a clearer thing to understand than trying to explain why keys now have a structure beyond just being the key to store the data under.
 
 #### Exposing persistable context in the TypedInput