It's Proof of the End of a Friendship (S01E02)

Title: The Final Chapter of a Friendship Plot: Iroha reflects on her desire to heal her ill younger sister, Ui, yet she finds no trace of her anywhere. Determined to uncover the truth, Iroha travels to Kamihama City in search of answers. Soon, she is confronted by a Witch but is rescued by three Magical Girls: Momoko, Rena, and Kaede. They share whispers of a mysterious Friendship Ending Staircase at Rena and Kaede’s school, suspecting it might be linked to a Witch. The group begins to delve deeper into the mystery, but their investigation takes unexpected turns...