- Ichioka Reina (一岡怜奈, leader) (Light Blue)
- Shimakura Rika (島倉りか) (Lavender)
- Nishida Shiori (西田汐里) (Hot Pink)
- Eguchi Saya (江口紗耶) (Yellow)
CHICA#TETSU was assembled between 2017 and 2018, beginning with the announcement that Hello Pro Kenshuusei member Ichioka Reina would debut as the leader of a new group. A second new group, also consisting of Hello Pro Kenshuusei members and later to become sister group Ame no Mori Kawa Umi, was beginning to form at the same time. A notice published on March 30, 2018 through the official Hello! Project website revealed that the groups would begin activities between summer and autumn 2018, and announced the "Hello! Project "ONLY YOU" Audition" from which those who pass could join either group. Several months later on June 9, 2018, three additional members from the Hello Pro Kenshuusei were added in a surprise reveal at the "Hello! Project Kenshuusei Happyoukai 2018 6gatsu ~Niji~" event in Tokyo; Shimakura Rika, Nishida Shiori, and Eguchi Saya.
The name of the group was unveiled on October 19, 2018 in a special Hello! Station web-show episode, where it was explained that CHICA#TETSU was created from a combination of the words "chica", meaning both "girl" in Spanish and "chika" (地下; underground) in Japanese, and "tetsu" from the Japanese word "tetsugaku" (哲学; philosophy), with the hashtag (#) representing the railway that connects the two. The intended meaning behind the name is "girls who think deeply about things", and they aim to give performances that are able to express the delicate and complicated emotions hidden in girls hearts.
Within the same announcement, it was revealed that both CHICA#TETSU and sister group Ame no Mori Kawa Umi, along with the yet to be announced audition winners, would come together to form a larger unit called BEYOOOOONDS (ビヨーンズ). The combined unit name has it's origins in the English word "beyond", meaning "to the other side of". The name was chosen with the feeling of wanting them to grow freely into the future.
- [2019.08.07] BEYOOOOONDS - Megane no Otoko no Ko / Nippon no D・N・A! / Go Waist (Regular Edition C #4 Toei Oedo-sen no Roppongi Eki de Dakishimete / CHICA#TETSU)