@broadstairs She is Tsurugi Miyuki (剣 幸) She was the Top Star of Tsukigumi in Takarazuka when Yurichan got her lead role when she was too young and nobody was helping her so the TopStar (13 years Yurichan's senior) helped her go through the role of Bill in Me and My Girl musical
The lady who came out was amami San's senpai (senior). She visited amami San on these show. I'll come back to translate the whole video. Though my Japanese is far from good enough.
They don’t explain the reason. I guess she was tired of pressure from the troop. She before said she accepted so many offers to perform main characters from the first year. Just guessing.