Mess class design

I have a class design that looks like this one:

When Main receives an item, properties of other items can change based on some rules. For example, if Item1 has a red color, item2.level must be 3. Sometimes a value can change properties of multiple items. Implementing all rules in Main class is possible but it's a mess code.

So, I have implemented the Aggregate class that include all items. When Main.setItem(item1) is executed, I update Aggregate with Aggregate.setItem1 and run Rules.updateAggregate that updates items of Aggregate according to all rules.

It works, but Rules class is very inefficient. Because it doesn't know which item has updated, it apply all rules all times. Also, updateAggregate method is very large and difficult to test.

Is there any better design?