Question: Which of these bands has had songs featured in several anime series, U2 or Flow?
Context: Etsuko Yakushimaru (やくしまる えつこ , Yakushimaru Etsuko ) is a Japanese singer, producer, and composer.  She is known for her solo works including theme songs in several anime series, such as "Arakawa Under The Bridge", "Space Dandy", "Sailor Moon Crystal", and "Mawaru Penguindrum".  As well as being the lead vocal of the rock band Sōtaisei Riron, she also works as an illustrator and narrator.  Initially, she did not reveal her face to the public, until the artist and her band was featured in the July 2009 edition of "Studio Voice" magazine.  She also goes by the alias of Tika α (ティカ・α ) when credited for lyrics and composing. This is a list of albums attributed to the anime adaptation of "My Bride Is a Mermaid".  There have been five soundtrack singles released for the anime which contained the opening, ending, and insert songs featured in the anime series.  There are six additional character song albums sung by the voice actors of six of the female characters. "Magical Girl Lyrical Nanoha" is a fantasy adventure anime and manga series written by Masaki Tsuzuki.  Set in a fictional universe, its storyline follows several different users of magic as they become involved with incidents related to powerful ancient artifacts.  Four anime series have been produced by Seven Arcs between 2004 and 2009 with music direction by Toshiki Kameyama.  The first season anime television series titled "Magical Girl Lyrical Nanoha" directed by Akiyuki Shinbo was broadcast in 2004 spanning thirteen episodes.  The second season of the anime series titled "Magical Girl Lyrical Nanoha A's" directed by Keizō Kusakawa was broadcast in 2005 spanning thirteen episodes.  A third season of the anime series titled "Magical Girl Lyrical Nanoha StrikerS" directed by Keizō Kusakawa was broadcast in 2007 spanning twenty-six episodes.  An anime film readaptation of the first season of the anime series was released in 2010.  The discography for these series consist of ten soundtrack albums, three compilation albums, nine maxi singles, one studio album, and fourteen drama CDs. "Hit in the USA" is a single released by Japanese band Beat Crusaders, and the song was used as the opening for the anime series "", and was later added to the "" full-length album in 2005.  "Hit in the USA" was released October 20, 2004.  They also released a maxi single, containing three songs featured on the anime series. Flow is a Japanese rock band, formed in 1998 and signed on to Sony Music Japan's Ki/oon Music label.  Flow is a five-piece band made up of two vocalists, a drummer, a bassist, and a guitarist.  As of February 2017, the band has released 31 singles and 10 studio albums.  Their songs have been featured in the opening sequences of several anime series. angela (stylized with a lower case initial) is a Japanese pop band, notable for having their music portrayed as theme songs for several anime television shows.  The main members are Atsuko and Katsu.  Their signature upbeat tunes and rich arrangements combine elements of electronica, dance, rock, swing jazz and ska.  In 2008, they started an alter ego band called Domestic Love Band (ドメスティック・ラヴバンド).  They are most well known for providing all opening and ending themes to the "Fafner in the Azure" anime series. This is a list of albums attributed to the anime adaptation "The Melancholy of Haruhi Suzumiya" based on the "Haruhi Suzumiya" light novel series.  There have been three soundtrack singles released for the anime containing the opening, ending, and insert songs featured in the anime series.  Three radio drama CDs were released, along with a single which contained the theme songs to the radio dramas.  A drama CD was also produced and the final track on the CD contained an original music track.  There are nine additional character song albums sung by the voice actors for not only the five main characters in the series, but four other minor characters were also given mini albums. U2 are an Irish rock band from Dublin formed in 1976.  The group consists of Bono (lead vocals and rhythm guitar), the Edge (lead guitar, keyboards, and backing vocals), Adam Clayton (bass guitar), and Larry Mullen Jr. (drums and percussion).  Initially rooted in post-punk, U2's musical style evolved throughout their career, yet has maintained an anthemic sound built on Bono's expressive vocals and the Edge's effects-based guitar textures.  Their lyrics, often embellished with spiritual imagery, focus on personal and sociopolitical themes.  Popular for their live performances, the group have staged several ambitious and elaborate tours over their career. Kenji Ohtsuki (大槻 ケンヂ, 大槻 賢二 , Ōtsuki Kenji , born February 6, 1966 in Nakano, Tokyo) is a Japanese rock musician and Seiun Award-winning writer.  His musical career began in the late 1970s.  He is the vocalist of Kinniku Shōjo Tai, Tokusatsu, Underground Searchlie and Karate Bakabon.  The lyrics of a Kinniku Shōjo Tai's song "Doko e demo Ikeru Kitte" affected the character design of Rei Ayanami, from the popular anime series "Neon Genesis Evangelion".  He's also performed the theme songs to several anime, including "Welcome to the N.H.K.", "Hellsing" and "Sayonara Zetsubou Sensei". Sandra Krasa is an American entrepreneur, producer and voice director for ADV Films on several anime series and movies and the founder and president of several companies.  She has also voice acted in a few titles, notably Layla Hamilton in "Kaleido Star".  Her anime directing credits include "Hello Kitty's Animation Theater," "MICHEL," "Blue Seed," and "Slayers."
Answer: Flow