The work on Reimu and Sanae may seem a bit unusual, but other than that the groupings in the cards are neat. Let's see... besides those grouped based on their debut games (the Windows series, of course), we've got the "Dynamic Duo" (Reimu & Marisa, of course), the "fighter originals" (Suika, Iku & Tenshi), the "chroniclers" (Akyuu & Rinnosuke), the "mischievous fairies" (Sunny, Luna & Star), & the "outsiders" (Renko & Maribel).
In Touhou "tradition" any playable character other than Reimu and Marisa would have to be bosses first. PoFV is the only game to introduce playable characters that were never bosses - Aya, Medicine & Yuuka (of course, the latter is a PC-98 alumna as final boss of Lotus Land Story, but the Windows series is widely considered as the "canonical" series, so yeah). However, Aya herself would reappear in MoF as Stage 4 boss, thus she fills the bill of "playable character & former boss". Besides, she also plays a very important role back in the said game.
Tasofro Spinoff Originals
Nagae Iku
Hinanawi Tenshi
Ibuki Suika
Suika came from Immaterial and Missing Power. Iku and Tenshi came from Scarlet Weather Rhapsody.The "Dynamic Duo"
Hakurei Reimu
Kirisame Marisa
PC-98 alumnae and main protagonistsUnidentified Fantastic Object
Byakuren and Followers
Hijiri Byakuren
Toramaru Shou
Kumoi Ichirin and Unzan
Murasa Minamitsu
Others
Tatara Kogasa
Nazrin (Shou's subordinate)*
Houjuu Nue*
* Later additions to the roster of Byakuren's followers.Mountain of Faith
Ascent to Youkai Mountain
Aki Shizuha
Aki Minoriko
Kagiyama Hina
Kawashiro Nitori
Youkai Mountain Patrol
Inubashiri Momiji
Shameimaru Aya*
Moriya Shrine
Kochiya Sanae
Yasaka Kanako
Moriya Suwako
* Aya first appeared in PoFV. Her appearance in this section refers to her major role as a senior patrol for Youkai Mountain.Imperishable Night
Household of Eientei
Houraisan Kaguya
Yagokoro Eirin
Reisen Udongein Inaba
Inaba Tewi
Forest Encounters
Fujiwara no Mokou
Kamishirasawa Keine
Mystia Lorelei
Wriggle NightbugThe "Chroniclers"
Hieda no Akyuu
Morichika Rinnosuke
Akyuu wrote Perfect Memento in Strict Sense and Memorizable Gensokyo. Rinnosuke's insights form the corpus of Curiosities of Lost Asia.Perfect Cherry Blossom
Encounter at the Forest
Letty Whiterock
Alice Margatroid*
Prismriver Sisters
Lunasa Prismriver
Merlin Prismriver
Lyrica Prismriver
Hakugyokurou
Konpaku Youmu
Saigyouji Yuyuko
Yakumo Household
Chen
Yakumo Ran
Yakumo Yukari
* Alice is a PC-98 alumna. This is her first appearance to the Windows generation.The Three Mischievous Fairies
Sunny Milk
Lunar Child
Star Sapphire
They are the heroines of Eastern and Little Nature Deity, Strange and Bright Nature Deity, and Oriental Sacred Palace.Phantasmagoria of Flower View
Debut Characters
Medicine Melancholy
Kazami Yuuka*
Gates to the Netherworld
Onozuka Komachi
Shikieiki Yamaxanadu
* Yuuka is a PC-98 alumna. This is her first (and so far her only) appearance in the Windows generation.The "Outsiders"
Maribel Hearn
Usami Renko
Music CD originals best known as one of the few, if not the only, humans from the outside world who knew of the existence of Gensokyo.Embodiment of Scarlet Devil
Encounter at Misty Lake
Rumia
Daiyousei
Cirno
Household of the Scarlet Devil Mansion
Hong Meiling
Koakuma
Patchouli Knowledge
Izayoi Sakuya
Remilia Scarlet
Flandre ScarletSubterranean Animism
Denizens of the Underground
Kisume
Kurodani Yamame
Mizuhashi Parsee
Hoshiguma Yuugi
Komeiji Household
Komeiji Satori
Komeiji Koishi
Kaenbyou Rin
Reiuji Utsuho