If Daru were a normal isekai character he'd be the one that gets kicked out of the party because he hid his power too much.
It isn't a very good story but it's exactly what it says on the tin:
This is a story that focuses on what happens in the main party when they kick out a member (in this case for his "own good") for being too weak but it turns out he's actually OP. You get some looks at what happens with the expelled character but they're kind of side stories. In the NORMAL story it's the opposite where the focus is on the expelled character and the side stories are of the original party struggling.
It's a failed attempt at an interesting take on the Expelled Party Member tale because people normally root for the underdog. With the twofer of this being poorly told and with nobody to root for there it just wanders. Stories with just people to hate usually don't work.
In a story you have to have someone in the main cast that you care about. It would have been better if the focus would have been on Athena. She could realize too late what Est meant to both the party and to her personally, and while trying to bring him back find that he's moved on from both the party and her. After this then you could have the party break up or take on new members to return to their former glory or whatever, and Athena could take up with whomever she cared to or with nobody because she can't get over Est.