She never wanted to marry the guy in the first place, and he clearly only gave the money to guilt trip her into marrying him. Of course she's not going to treat him as some kind of savior. Nobody would treat someone as a savior in that situation.
Exactly.
Ryuu exploited Koharu's desperation to get her under his thumb. Then he acted like she owed him sex because of the amount he
chose to pay (she never agreed to any such deal). And the first time she made a small gesture of friendly, relationship-building trust toward him, he molested, degraded and all but raped her in the bath.
As presented so far, Ryuu is a scumbag. He's a narcissistic man-baby who doesn't give a shit about anything or anyone beyond the satisfaction his own desire. That people give him a pass while wishing death on Koharu for not happily becoming his #3 sex pet is mind-boggling to me.