2004:
Formed by Hazuki, Reo, and Asana.

2006:
Guitarist Yusuke joined.

2010:
Released their final indie single 'JUDGEMENT'. At the final performance of their last indie tour, bassist Akinori joined.

2011:
On 1 June, released their major debut album I BELIEVE IN ME. On the release day, they staged a guerrilla live show in Shinjuku Kabukichō. Later that year they performed at Akasaka BLITZ, and in 2012 at Zepp Tokyo, steadily moving on to larger venues.

2015:
Their 10th anniversary best-of album 10th ANNIVERSARY 2004–2014 THE BEST reached No. 5 on the Oricon Daily Chart.

2016:
Appeared at the large-scale festival VISUAL JAPAN SUMMIT 2016. In December, Akinori departed, resulting in a temporary suspension of live activities.

2017:
In April, resumed activities with a one-man concert THE JUDGEMENT DAY at Shinkiba STUDIO COAST. In May, released SINNERS-EP and concluded their nationwide tour at Hibiya Open-Air Concert Hall. In December, at the countdown event lynch. COUNTDOWN LIVE ‘2017–2018’ in their hometown Nagoya, Akinori’s return was announced.

2018:
On 11 March, held their 13th anniversary concert lynch. 13th ANNIVERSARY -Xlll GALLOWS- [THE FIVE BLACKEST CROWS] at Makuhari Messe, once again becoming a five-member band and attracting 6,000 fans. In June, appeared at LUNA SEA’s festival LUNATIC FEST. 2018. At year’s end, performed for the first time at Japan’s largest rock festival COUNTDOWN JAPAN 18/19. In July, released their 13th album Xlll.

2019:
Hosted their own two-day event BLACK BEAUTY BEASTS at Zepp Nagoya, featuring Arlequin, Angelo, D’ERLANGER, RAZOR, Merry, MUCC, and SUGIZO. In August, made their debut at ROCK IN JAPAN FESTIVAL 2019.

2020:
In March, released their 14th album ULTIMA. In April, to support live houses struggling during the COVID-19 pandemic, issued the charity single OVERCOME THE VIRUS, distributing ¥11,786,297 in profits to 149 venues. In October, staged their first audience-attended performance in around eight months at Hibiya Open-Air Concert Hall. On 23 December, released their first digital single ALLIVE.

2021:
On 29 January, announced the cancellation of their planned Nippon Budokan concert owing to the pandemic. In February, held the streaming performance THE RESISTANCE, drawing a peak audience of 12,500. From May to July, undertook their nationwide tour TOUR’21 -ULTIMA-, completing 14 shows including rescheduled dates. On 11 June, marked the 10th anniversary of their major debut. On 27 December, released 2011–2020 COMPLETE BOX [Limited Edition], containing all singles, albums, and music videos issued via King Records. On 31 December, following their anniversary concert THE IDEAL, announced a temporary hiatus.

2022:
On 11 September, announced their return and the rescheduling of the Nippon Budokan performance for 23 November. On that date, successfully staged their first-ever one-man show at Budokan, THE FATAL HOUR HAS COME.

2023:
In March, released REBORN, a bold work featuring compositions from all members for the first time in three years. From 4 March, embarked on the nationwide TOUR’23 “REBORN” across Zepp venues. That same month, released the Budokan performance on Blu-ray and DVD.

2024:
In June, issued the mini-album FIERCE-EP. From July, launched the 15-date nationwide tour TOUR’24 “THE FIERCE BLAZE”.

2025:
Celebrating their 20th anniversary with the lynch. XX ANNIVERSARY PROJECT, comprising 10 special features. As XX act:4, in April they released the retake albums GREEDY DEAD SOULS, UNDERNEATH THE SKIN and EP GOD ONLY KNOWS. On 24 September, as XX act:8, will release their second batch of retake albums THE AVOIDED SUN, SHADOWS and EP BRINGER. The project will conclude with the XX FINAL ACT, a performance at Tokyo Garden Theater on 28 December.