Mikuni honestly ruined this manga. At the end of the day, she's nothing more than a horney, jealous ball of piss perversion. Sound similar to the sisters? Well, it's not. Ya, they would kind of force themselves on the mc, but the mc was just a walking coward to begin with. When he got into a relationship they kind of stopped out of respect for Keita and the teach. Of course, this didn't last long and they were back to kissing in no time since the sensei, being a noob herself and not claiming her rights as his partner, Keita also a cheating coward, started kissing his sisters and doing ecchi shit with them again. Mikuni, on the other hand, tried to force herself on him more even after knowing that fact and Keita eventually let her do just about anything she wanted. She honestly had no business even being apart of what was going on. She was like the 5th wheel in all this and thought she should be allowed to just jump right in there.
I admit, I'm not reading this for the romance since this literally butchered, shat on and raped the sensei ship and sunk it into the Marianas Trench. And whatever "romance" that comes out of this I no longer care for since Keita has proven to be a shitty choice for a partner. All the females (except the sensei) have proven that they would do anything to sate their lust; so either this ends in a harem (it won't) and they all just vent their lust on the Keita. Or he gets with Mikuni since Keita is all but guaranteed to cheat on his partner in the future and with her track record, she probably has a cuck fetish as well. Pair the shittiest characters together honestly.