I am making a web application with rails.
I encountered an N + 1 problem and started using includes.
I asked a question without knowing the following method.

• There are two models, Group and User
• User belongs to any one group (associated)
• Read both tables as Group.includes (: user)
• At this time, the child table user wants to read only males
• I want to read both parent tables

Group model

id	name
1	Group A
2	Group B

User model

id	name	Group id	Gender
1	Taro	1	Men
2	Hanako	2	woman
3	Jiro	1	Men

Error message

If i search, you will see that the child table is used to narrow down the parent table.
I couldn't find a way to narrow down only the child table without narrowing down the parent table.
(Did you find it?)
If i execute the following, only GroupA can be extracted, and the parent table Group wants to output both A and B.

Applicable source code

※ Simplified

Rails
## controller
@groups = Group.includes (: users) .where (gender: male) .references (: users)
## view
@ groups.each do | group |
  group.name
end

I tried to try

scope etc. but it didn't work and I would appreciate your advice.

Supplemental information (FW/tool version etc.)

The Rails version is 5.2.2.
DB is developed with mySQL, cloud9.