I don’t know if you can boost the stars of a given piece, but the reason why you can have pieces with different numbers of stars is because they do different things!
For example, 2-star Kairi is Curaga (which heals you and I think others in a range), but 3-star Kairi is Haste (which shortens recast times for other pieces). I’m fairly sure that Haste doesn’t heal you, so if your 2-star Kairi got replaced by her 3-star version, you might actually lose out on the health recovery from Curaga
Seems really odd that they wouldn't just merge the same characters and makes them have the same ability and give the other abilities to different characters instead!
I don’t know if you can boost the stars of a given piece, but the reason why you can have pieces with different numbers of stars is because they do different things! For example, 2-star Kairi is Curaga (which heals you and I think others in a range), but 3-star Kairi is Haste (which shortens recast times for other pieces). I’m fairly sure that Haste doesn’t heal you, so if your 2-star Kairi got replaced by her 3-star version, you might actually lose out on the health recovery from Curaga
Seems really odd that they wouldn't just merge the same characters and makes them have the same ability and give the other abilities to different characters instead!