The younger ML simps hard, but is unable to get past the superior/apprentice barrier. Until the MC dies and comes back as younger than himself and with a lower rank in a different body. Even after ML figures out it's him though, he still waits for consent. Their swapping of hierarchy actually brings balance to their relationship. They've both had years of experience on the battle field now, gone through excruciating grief, and learned to rely on each other emotionally, even if they still have communication/trust issues.

Seeing how much the ML cares for and supports the MC, through tender domesticity and little acts of service, especially during the MC's more serious depressive episodes... it genuinely made me emotional.

In the last arc, an incident happened and many guides were killed and everyone in military base was blaming him. His 'good' research friend knew this and still told MC to get lunch from the canteen by himself. Ofcourse the MC was humiliated. Keep in mind this is military setting and his friends are suppose to be in high positions. YOU THING they would have some brains. Also, they never went out of their way to even attempt to investigate his death--some friends they are. ONLY the ML did...

He was explained to be a good teacher to many guides. These guides never show up in the story. He also had an opportunity to teach some new B level guides in his new life but nothing came of that. It would've been cute to see him not being able to help himself and end up teaching them. Then in the scenes where everyone was blaming him, these students could've stood up for him and defend his character. If his good friend also put in a few words for him, than it would've feel natural for people to go "oh maybe we were wrong to jump to conclusions, he has so many people defending him."