Year 0: In the past, as a child, Shirou Emiya survived a magical catastrophe which killed thousands, where he is the sole survivor. This causes him to swear to devote his life to saving EVERYONE, without care to what happens to himself.

Year 100: In the future, the “spirit of the planet” offers Shirou (now called Archer) a deal to act as it’s “Counter Guardian”, in order to save the planet. He agrees. Later on, he finds out this deal requires him to kill large numbers of people to who are causing acts of destruction to the planet. Bitter and disillusioned, Archer regrets his younger self's ideals.

A magic object allows Archer to travel back in time in an alternate universe to year 50 and confront his previous self. He has a choice between whether or not to kill this younger self.

Killing Shirou Emiya does not change Archer's past, but it does stop his alternate, younger self from a life of unimaginable pain.

Demonstrative military retaliation refers to a doctrine where the state responds to cross-border attacks or provocations with visible, limited, and targeted military action. Strategic restraint refers to a doctrine where the state deliberately avoids overt military escalation in response to provocations

Hamlet is the son of a medieval King of Denmark. After the sudden death of his father, his mother marries his uncle Claudius, who becomes king. One night, Hamlet has a vision in which the ghost of his father appears to him and tells him that he was murdered by Claudius in a plot to take the throne. The ghost tells Hamlet to kill Claudius to avenge his death.

Collectivism refers to the prioritisation of the collective of individuals, where society's or community's interests are considered more important than an individual's interests