Kousoku Inran Jugyou Maid-tachi no Shigoto

A relative of Mayu notices changes in her behavior and sends family maid Kana as a transfer student to the same class to watch after Mayu. The school kingpins aim to make Kana a slave, but since they lack any compromising materials, they plan to use obedient Mayu to break the will of Kana.

[From vndbreview]