Seirei Tsukai no Blade Dance - Vol. 2 Ch. 11

[MangaDex]

 

[Kaarme]

I'm starting to get the picture: Claire's sister was also maniacally hungering for power and didn't care about the consequences, thus dooming her whole clan and land. It must run in the family, considering Claire here was willing to let all those people present to suffer and even die, just to gain some power. She doesn't need to win the blade dance festival to ask her sister why she did it. Claire only needs to look into a mirror to see the answer.