
While your analogy is interesting, a gun is an instrument without a will of its own. It's triggered in accordance with its handler.
Ageha, on the other hand, is his own person (has a will of his own). As such is the case, takuto and ageha would be accomplices in their crime.
Takuto cheats on his wife
Ageha doesnt end his relationship, leading to the affair
The wife, so far, seems innocent
Based on the facts above, Takuto and Ageha are both reprehensible as per social morals. They realize this, and act accordingly. Hiding the affair, meeting secretly, and etc.
While it is true that cheating is wrong, it is also wrong to allow one to cheat.
A better analogy would be: A person is being bullied in front of an audience. The audience just looks on/ doesn't participate. The bully is certainly at fault, but so is the audience in allowing the bullying to continue by not restraining the bully. Multiple reasons could stop the audience from participating, and I wont be the judge for that. In the end, the person being bullied will continue to be bullied. Both parties are hurting this individual (one directly and the other indirectly).
This is just on a smaller scale. The Holocaust, one of our world's greatest tragedies, is an example on a larger scale.

"This is just on a smaller scale. The Holocaust, one of our world's greatest tragedies, is an example on a larger scale."
Hooray for Godwin's Law.
Could've easily stopped at the bullying anology and deliver your point.
There are a lot of people who lost their lives trying to stop Hitler. Ther are still veterans carrying trauma from that time. They did not stand aside and do nothing. My great grandparents from both sides and grandaunts and uncles all sacrificed to stop Hitler. I resent to think that people would think they haven't done enough to stop Hitler's bullying.

I wasn't trying to undermine the efforts that went into stopping Hilter. It's just when Hitler initially started persecuting the Jews, many decided to not intervene. Only when it escalated and their own citizens were being threatened did people start to work against Hilter and his cause. A lot of politics went into a country's reason to enter a war. Also, I am guilty for using Godwin's Law but it doesn't make it any less true.
Blame blame and more blame!!!!!
Like, are you serious?
You deluded people can't seem to do the math on your own, so let me help you
Ageha and that bastard Tokuto have been friends for longer then the wife even knew him
+
lonely melancholic that so obviously only has Tokuto
+
Ageha's obvious heartbroken behavior during the wedding
+
Ageha's hatred for affairs
=
*this has been going on for longer then Tokuto's relationship with ms wife
*he would have cheated anyway
*Ageha is so in love with Tokuto he lets himself be used
*unless Ageha raped him, it is so obviously Tokuto's fault, using a kind soul for his twisted amusement while hurting the woman he swore loyalty to
*Tokuto is making a conscious decision to cheat and lie and hurt, only coming to see Ageha when he wants sex
*you can not make someone cheat on their wifehusbandboyfriendgirlfriend
they do it themselves -unless you drug then jump them, which is considered rape-
Yet this is Ageha's fault? What the hell is it with people that makes them think the married one is innocent? Ageha's not CHEATING on anybody, he isn't -despite what most of this planet's fucked up people think- HURTING anybody, HOKUTO IS
If someone -Hokuto-,
kills another -ms wife-,
with a gun -Ageha-,
Is the gun, going to trial?
NO!!!!! Because the GUN was FIRED, the TRIGGER was PULLED, a HAND PULLED the TRIGGER, and that HAND'S OWNER is at FAULT!