This is a bonus episode. It exists because someone at the studio decided fans who bought all six volumes deserved fanservice in a hot spring, no apologies. The show stops pretending to have a plot and just lets its cast be stupid and comfortable with each other, which is exactly what Dog Days'' fans showed up for.

Dog Days'': Limone Resort Tenbou Onsen! is a single-episode OVA from 2015 connected to Dog Days''. It was offered as a bonus to buyers who pre-ordered the full set of six Blu-ray and DVD volumes of Dog Days''. As the title indicates, it centers on a hot spring at Limone Resort, and it pairs the franchise's fantasy setting with ecchi content.