Undergirls

the Undergirls (アンダーガールズ, or Under Girls) are an special group/team of girls that since the term was included in the 1st Senbatsu Election, take charge of the main c/w (B-side) of most of the AKB48 Singles and recently also SKE48 Singles.

History

the Undergirls were introduced in the 1st Senbatsu Election, where the girls that ranked from 22# until 30# were given the chance to do the b-side track of the single (Iiwake Maybe) that the senbatsu elected (21#~1#) were going to sing.

previous to this, all the original b-sides included were also done by the Senbatsu of that single, what now gave to a lot other girls the chance to actually take part of a single release (with most of the them for their first time).

the first Undergirls generation, consisted of 9 girls and sung the track Tobenai Agehachou, which also got a video. marking it as the first time an AKB48 c/w got a Music Clip.

later on for the next single RIVER (that also introduced the Theater Girls), the Undergirls concept was used again. with the difference that this time, the mannager decided the members making an almost completely different selection of girls compared to the first generation.

the Undergirls weren't used in Sakura no Shiori and made a comeback in Ponytail to Shushu --and were used on streak until Beginner, giving the total of "Undergirls songs" to 5.

Undergirls on SKE48

for SKE48's 3rd Single Gomen ne, SUMMER, the Undergirls concept was implemented with SKE for the first time.

in difference with AKB, 2 different groups of Undergirls were used in the same single ("Undergirls A" and "Undergirls B"). both groups featured 7 girls and different songs, Undergirls A was an Exclusive-track and Music Video of Type-A, as Undergirls B were of Type-B.

"Undergirls" as Popularity level used by the Fandom

The Undergirls are usually given most of the spotlight after the Senbatsu, making the other Single-exclusive group (the Theater Girls) "feel" as the "least important" group of girls for the manager.

the Theater Girls were introduced in RIVER, a single that was promoted as "first single ever where all the 48 girls of the group take part". with Senbatsu still being "the most important" selection of girls, the Undergirls were used once again and a new group named the Theater Girls was introduced. (see full article: Theater Girls)

in difference with the Undergirls, the Theater Girls didn't get a new original song and got to cover an AKB48 Stage Song instead. -as well as getting their pv filmed in the AKB48 Theater as a performance, instead of an "original PV" like the Undergirls or Senbatsu get. (what makes it feel as if the Theater Girls "don't get as much budget as the Undergirls")

not only for this, the Fandom sometimes notice how some girls are pushed more than other from the manager. and if those girls aren't popular enough, they mostly end up taking part of Undergirls instead of Theater Girls.

since the Type-A and Type-B releases were included in AKB48 Singles, the Theather Girls started to take part of only one of the editions, compared to the Undergirls that appear in both.

other difference between both groups is that the Undergirls are more of an actual regular subgroup, while the Theater girls don't necessarily appear in all the singles (specially in those where the Senbatsu Elections are involved)

in the AKB fandom, you will normally see fans classificating the girls as "Senbatsu" "Undergirl" or "Theater Girl" , referring actually more to popularity-level instead of how much they are pushed by the manager. (always depending on the context, of course)

Undergirls Generations (AKB48)

1st Generation

Tobenai Agehachou (Iiwake Maybe) (9 Members (22#~30#))
Team A: Takajo Aki (23#)
Team K: Ohori Megumi (24#) · Masuda Yuka (25#) · Matsubara Natsumi (30#)
Team B: Yonezawa Rumi (22#) · Hirajima Natsumi (26#) · Sashihara Rino (27#) · Katayama Haruka (28#)
SKE48, Team S: Matsui Rena (29#)

2nd Generation

Kimi no Koto ga Suki dakara (RIVER) (16 Members)
Team A: Oota Aika · Katayama Haruka · Kuramochi Asuka · Sashihara Rino · Takajo Aki · Maeda Ami · Nakagawa Haruka
Team K: Kikuchi Ayaka · Fujie Reina · Nito Moeno
Team B: Oku Manami · Ishida Haruka · Sato Amina · Sato Sumire · Komori Mika
SKE48, Team S: Matsui Rena

3rd Generation

Nusumareta Kuchibiru (Ponytail to Shushu) (16 Members)
Team A: Iwasa Misaki · Oota Aika · Katayama Haruka · Kuramochi Asuka · Sashihara Rino · Maeda Ami
Team K: Akimoto Sayaka · Kikuchi Ayaka · Nito Moeno · Fujie Reina
Team B: Oku Manami · Komori Mika · Sato Amina · Sato Sumire
SKE48, Team S: Matsui Rena · Yagami Kumi

4th Generation

Namida no SeeSaw Game (Heavy Rotation) (18 Members (22#~40#))
Team A: Oota Aika (22#) · Katayama Haruka (37#) · Kuramochi Asuka (22#) · Matsubara Natsumi (39#)
Team K: Umeda Ayaka (32#) · Nito Moeno (29#) · Fujie Reina (33#) · Yonezawa Rumi (34#)
Team B: Ishida Haruka (27#) · Komori Mika (30#) · Sato Sumire (31#) · Hirajima Natsumi (26#) · Masuda Yuka (25#)
AKB48 Kenkyuusei: Shimazaki Haruka (28#) · Yamauchi Suzuran (36#)
SKE48, Team S: Oya Masana (24#)· Yagami Kumi (38#)
SKE48, Team KII: Takayanagi Akane (35#)

5th Generation

Boku dake no value (Beginner) (23 Members)
Team A: Iwasa Misaki · Oota Aika · Katayama Haruka · Nakagawa Haruka · Maeda Ami
Team K: Kikuchi Ayaka · Fujie Reina · Nakatsuka Tomomi · Nito Moeno · Matsui Sakiko · Yonezawa Rumi
Team B: Ishida Haruka · Oku Manami · Komori Mika · Sato Sumire · Hirajima Natsumi · Miyazaki Miho
SKE48, Team S: Kizaki Yuria · Yagami Kumi
SKE48, Team KII: Ishida Anna · Takayanagi Akane · Mukaida Manatsu