Short answers, pulled from the story.
The Group Sounds movement began in 1966 when the band The Spiders performed in the Netherlands. This era was characterized by Japanese musicians replicating American and British rock sounds while singing in English.
Happy End released their self-titled debut album on the experimental record label URC on the 2nd of August 1970. This release challenged the prevailing belief that Japanese rock could not be sung in the Japanese language.
The Flower Travellin' Band moved to Canada and published their first album of original material, Satori, in April 1971. This album is now considered a progenitor of heavy metal music and doom metal.
X Japan released their second album Blue Blood in April 1989. The album reached number 6 on the charts and sold 712,000 copies, marking the beginning of a new era for Japanese rock.
Aldious topped the Oricon Indies Albums Chart with their debut album Deep Exceed in 2010. This achievement is cited as the initiator of the girls metal band boom in Japan.
Babymetal began their world tour at London's Wembley Arena in 2016. Their album Metal Resistance reached number 15 on the UK Albums Chart, marking the highest ever entry by a Japanese act.