Hakudaku no Aoki Erena ~Shaseishitara Fuuin ga Tokeru Nante Mushiro Gohoubi Desu~

At St. Elencia Academy, student Makoto Yasuno accidentally revives an ancient goddess, Elencia, who had been sealed away in the school’s towering spire. As a result, he’s forced to equip a cursed artifact called the “Aries Chalice”… on a very specific part of his body.
To remove the chalice, Makoto must form a bond with Satsuki Toudou, a classmate and descendant of the family that originally sealed Elencia. This involves, well, repeatedly engaging in intimate acts with her while the chalice is still attached. Only then will the seal on Elencia be broken, and the chalice removed.
Reluctantly, Makoto agrees to Elencia’s demands and approaches Satsuki. However, the Toudou family catches wind of his plans and sends Satsuki’s best friend, Kotone Kuroishi—a descendant of the Toudou family’s long line of guardians—and other assassins to stop him.
Will Makoto succeed in breaking the seal and freeing himself from the chalice’s curse?

[Translated from dlsite]