Si☆4

 (read as Si Four) was an indie local idol group created by BONAMII Inc. (or Bonamii Model Production).

The group was originally formed in July 2013 as St.☆Bonapro Gakuen (聖☆ボナプロ学園). They disbanded in November 2014 and reformed as Si☆Stella the next month. The name means "Si(ster) Stella(r stars)". They made their live debut on December 21, 2014.

In August 2018, Si☆4 was created as a sub-unit. Si☆Stella disbanded in December 2019, and Si☆4 became its successor group. Si☆4 disbanded on April 29, 2022.

Final Members

 * Kashiwa Ayana (柏綾菜; ) (Joined December 2014)
 * Kashiwa Yuina (柏結菜; ) (Joined December 2014)
 * Furuoka Koharu (古岡瑚遥; ) (Joined February 2016)
 * Sugawara Miina (菅原みいな; ) (Joined August 2018)

Former Members

 * Ishikura Miyuu (石倉未悠) (Founding member, graduated December 2013)
 * Yoshikawa Rio (吉川莉央) (Founding member, graduated December 2013)
 * Ishikawa Suzuka (石川鈴果) (Founding member, graduated March 2014)
 * Ishikawa Yumeka (石川夢花) (Founding member, graduated March 2014)
 * Yoda Ayaka (依田彩花) (Founding member, graduated June 2014)
 * Ohashi Remi (大橋礼実) (Joined June 2014, graduated August 2014)
 * Marumoto Rin (丸本凜) (Joined December 2013, graduated October 2014)
 * Imamura Misato (今村美里) (Joined June 2014, left November 2014)
 * Amano Mimi (天野みみ) (Joined June 2014, left November 2014)
 * Amano Misaki (天野美咲) (Joined June 2014, left November 2014)
 * Mafune Nono (真船乃暖; ) (Founding member, graduated August 31, 2015)
 * Akai Sakura (赤井桜; ) (Joined September 2014, graduated June 12, 2016)
 * Sakurai Rico (櫻井理子; ) (Founding member, graduated December 23, 2016)
 * Nakamura Yuuhi (中村柚陽; ) (Joined October 2015, graduated July 8, 2017)
 * Masuda Hina (増田陽菜; ) (Joined December 2014, graduated November 5, 2017)
 * Kikuchi Yua (菊地結愛; ) (Graduated March 19, 2019)
 * Okafuji Lulu (岡藤瑠々; ) (Graduated September 6, 2019)
 * Yajima Ayano (矢島彩乃; ) (Joined June 2019, left December 2019)

Sub-groups

 * BONAMETAL (Mafune Nono, Akai Sakura, Sakurai Rico, Masuda Hina, Kashiwa Ayana and Kashiwa Yuina) (2014-2018)
 * Si☆4 (Kashiwa Ayana, Kashiwa Yuina, Furuoka Koharu and Sugawara Miina) (2018-2022)

Trivia

 * They were being promoted as the youngest idol group when the group first formed on December 21 2014.
 * The eldest Si☆Stella members Kashiwa Ayana and Kashiwa Yuina are fraternal twins.