Under tale:G why did dad kill sans?

The relationship between sans and gaster is not directly shown in the game. Sans is considered to have a lot to do with Gaster. Like Sans, Gaster speaks in a special font different from others, namely Wingdings font.

In the 42 media reviews provided by Metacritic, the average score is 92. Ranked 3rd in PC games released on 20 15. Ranked 8th among all platform games released in 20 15 (including Wizarding 3 and MGS 5, which were released on multiple platforms twice).

Game background:

A long time ago, the earth was ruled equally by two races, namely, humans and monsters. One day, the drums shattered the peace between the two sides; Under the aggression of near-slaughter, mankind has won great victories. Humans banished the monster to the underground world, and seven wizards set up a rather powerful magic barrier to trap the monster in the underground world.

People can enter the lower bound at Mount Ebert, but they need at least a human soul and a monster soul to leave the lower bound. Before the story began, no one left the lower bound alive, which led to rumors that the climbers on Mount Albert had left and never came back.

The monster is trapped in the underground world and ruled by Asgard Drummond. After the monster dies, the body will immediately turn to ashes, without soul and body. Monsters' souls are far less powerful than human beings.