Yes, It Goes Around Every Year

As Sera goes to a meeting with the other vampires, Eucliwood comes down with a fever, so Ayumu and Haruna spend the day looking after her. The next day, Anderson explains that Eu's symptoms came from eating too much tangerine pith, which is considered poisonous to denizens of the underworld, and resort to bizarre remedies to get her back to health. Afterwards, Haruna catches a cold from overworking herself so Ayumu and Eucliwood look after her instead.