Island you must visit when travel to Yilan

Believe me, the scenery at Guishan Island is stunning. Most of the ecosystem there is well preserved due to there being only less than 20 people, mainly the military service volunteers who will stay there for a long duration. There is also a choice to join the SUP activity there, but due to the late reservation and time constraints, I didn't join. I will definitely join it next time I visit.