"Following the events of Urban Legend in Limbo, a weird spider-looking probe crashes into Youkai Mountain and started to roam around. Reimu and Sanae decided to investigate the probe and found out it was of otherworldly origin. And worse, trees withered and mist fades as the probe passes by. At Eientei, Eirin Yagokoro and Kaguya Houraisan are fully aware that this day would come for the Lunarians to take action to invade Gensokyo. In response, they prepared a special medicine and asked Reisen to deliver it to Reimu and her friends. Meanwhile, Marisa is still studying about the Occult Balls, finding out why one of them is different from the others as Reisen appears with the medicine. With Gensokyo facing a new crisis, Reimu and the others must stop the one behind the incident."