Due to a family feud, Setsugetsuka holds a deep grudge for Haruka for unknown reasons. In middle school, Setsugetsuka was nicknamed "Empress Of Seijukan" at Seijukan Girls Acadamy. When Haruka's hobby was exposed of her being an otaku, Setsugetsuka threatened the entire school including Haruka's three best friends that she's known since elementary to isolate her.
In the series finale, Setsugetsuka appears and is gloating over having been able to cause Haruka's misfortune trying to take away her happiness for her future forcing Haruka to get married to her family's second eldest son to assume victory. Her plan was to become the next head of the Tennouji by expelling Haruka from the Tennouji family and backing of the Nogizaka family's power. However, when Setsugetsuka finds out that Gentou's and Akiho's set up to test how strong the bond between Yuuto and Haruka truly is so that they can make an official wedding for them, Setsugetsuka's plan backfires and steps in to interfere trying to ruin everything by summoning the Tennouji clan's premier security force, Cerberus, but learns that her Cerberus has already been dealt with by Touka and her squad much to her horror, thus accepting defeat and being known as the former next head of the Tennouji family.
- It may be hinted that Setsugetsuka may have found out about Haruka's and Yuuto's relationship and planned to break them apart to achieve her goal.