In the miraheze wiki, Sword is referred to as “socially awkward and immature”; yet also “heartfelt”, with “a tendancy to speak without thinking first”. They are also described as “faithful towards his friends, and hypes them up for anything that comes their way.”  I personally imagine that Sword would commonly use a more upbeat tone when speaking.  -  quotations have been sourced from:  https://phighting.wiki/Sword/Lore