The Genius of Sappheiros Weekend 3.0 　

Plot Point: It's a normal day in Gensokyo when Reimu Hakurei notices a strange fog rolling in. All across Gensokyo, residents witness this fog weakening and killing a great many lesser youkai. At the behest of Yukari Yakumo, she joins forces with Marisa Kirisame, Sanae Kochiya, and Aya Shameimaru to investigate the fog's appearance... (from Touhou wiki)
How it Works: You choose a party of 5 characters, with a 6th character, the Commander, helping out via support abilities. You head though various dungeons (also called Stages) and fight enemies in turn-based RPG-style combat. As you win battles you gain experience and level up, sometimes learning abilities. However, you also earn "Power" as you level up, and these points can be put, and taken out of, into 14 different categories (4 personal, 4 weapon-types, and the 6 stat types) to increase your stats or learn other abilities.

 

Extra EXTRA notes

Unlocking Fujiwara no Mokou early: After visiting Akyuu for the first time, talk to her again. The Bamboo Forest maze will appear to the west; head there, and travel through the forest in accordance with the Konami Code (Up, Up, Down, Down, Left, Right, Left, Right) to find Mokou.
Unlocking Byakuren Hijiri early: Head to Myouren-Ji, the building in the southeast where Minamitsu Murasa is standing. Wait in this building for a full hour of real time and a cutscene will trigger in which Byakuren will join.

You do not need to visit the SDM, Stage 1, (or visit Akyuu for Byakuren) to unlock those characters. However, it must be noted that the player must visit Akyuu once more after getting the recipes in order to unlock Mokou. Also, they will automatically join your party right before stage 9 (Mokou) and 11 (Byakuren) respectively if you do not recruit them before then. (~ Taken from the Touhou Wiki, and shortened slightly for space)