Ore no Shibou Flag ga Todomaru Tokoro o Shiranai - Ch. 91 - What I Wanted to Entrust

[Kaarme]

Just because he tries to be hated doesn't mean that's how it will end up, it'd probably end up similar to Erica with an initial negative reaction before something esle comes to light that flips it 180. As for why he's doing this, well he's pretty sure he's going to die soon anyway due to the cursed sword so I don't think he'd really care if he's hated more if it means he can save the world. And why he'd think making the two hate him would put them at odds with Erica, I think he's still under the impression Erica doesn't know of him saving Colette and that she doesn't actually like him but is following him out of some sense of obligation thanks to his helping their family and the whole engagement.

He's not using the cursed sword often at all, unlike the game Harold. He doesn't need to because he's far stronger than the game Harold. It's not shortening his life significantly. Justus merely believes it is because he has no idea how strong Harold is and thus thinks Harold can only handle his tasks by using the sword.

I'm not sure how dense (stupid) Harold is, but his relationship with Erica isn't anymore as bad as it used to be. He can have real discussions with her. Too bad it doesn't happen often and he's still actively trying to push her away. However, that's still a far cry from the game situation where Harold was Erica's enemy through and through. Harold is relying on the Sumeragi intelligence apparatus, so it would be pretty weird if Harold kept thinking Erica knows nothing. If he managed to make Erica join Liner & Colette, then he will also accept the fact Erica will learn Colette's mom is alive and well. The cohesion of that party would be kind of dubious if Erica knows Harold is a good guy infiltrating Justus's operation, while Liner would believe Harold is thoroughly rotten, and Colette wouldn't know what to believe.

If Harold wants to help Liner & Co save the world, it would be easier if Liner doesn't hate his guts.