Hmm...
The samurai would.
Seppuku is done to atone for a major transgression, or as a punishment. It had no glory attached at all, and was not something that would be sought out at all. The irony is that the lead character is reading Hagakure, a tome that is responsible for a lot of the romanticisation of the act, but even that goes to pains to point out how much it is to be avoided if it can be. The last thing a samurai wanted was to be asked to act as kaishaku, as there is no glory in doing it well, and a complete loss of reputation if you do it badly.
It was NEVER a way to avoid personal suffering. In fact, that would be considered cowardly, and the samurai who opted to take that option would leave his descendents destitute.
No, it wasn't. It was a very inaccurate representation of a culture that was completely misunderstood. The only beliefs here are those of the film-makers who have no clue what they're depicting.
And even less to do with the samurai, Japan, or anything close to that culture.
This isn't "assisted suicide". The point of seppuku is to endure the pain as an act of atonement for a major problem caused by you (or that you're taking the blame for, at least). This is... nothing to do with it.
Then he's an idiot, a fool, and a mindless cretin. If Micah wants to avoid the torment of the cancer, he has options. This is just ego, romantic fantasy, and a degradation of the actual act. It is the opposite of giri... actual giri in this case would be to smack Micah upside the head, scream at him to grow the hell up, get over his martyr fantasy (which is not achieved at all), get out of the idea that he's some ancient samurai he obviously has no clue about, and, if he insists on going ahead, walking away and washing his (Ray's) hands of the lunatic of a "teacher".
Oh, and showing Kaishaku at the end (odd version, but still)???? No, incredibly inappropriate.
Fools showing that they have no idea or respect for the culture they're aping without understanding. Not good.