Need to delete attached email in super user account

Need to delete attached email in super user account

Dear Support Team,

I have my super user setup with the email id:  nisuventures@gmail.com.

When creating and assigning admin and other user accounts, one particular account ( sumanth@cafecups.in) has been assigned with super user account nisuventures@gmail.com (Pic1)

I intend to use  sumant@cafecups.in for personal use and i want it to be a separate USER. 

I tried to edit in super user account but no luck. sumanth is not editable. (Pic2)

Could you please help me to remove  sumanth@cafecups.in so that i can setup new email account.

Please find the attached screenshots for your reference.


Thank you.
Sumanth