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Short answer no, you can get to know a character very well without actually getting invested in them, especially if the character is "a bit of a tool". To get people to care about a given character...
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Source: https://writers.stackexchange.com/a/39101 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
Short answer no, you can get to know a character very well without actually getting invested in them, especially if the character is "a bit of a tool". To get people to care about a given character you need them to relate to that character. The reader should feel that in the same situation as the character they would have done just the same thing. It often helps if the character is also endearing and "likable" as well as relatable but it's not required.