You can find a lot of hits if you use the following japanese headline: 新型コロナ ワクチン 心筋炎「重大な副反応」 厚労省、警戒度上げ Among them this one: https://mainichi.jp/articles/20211

You can find a lot of hits if you use the following japanese headline: 新型コロナ ワクチン 心筋炎「重大な副反応」 厚労省、警戒度上げ Among them this one: https://mainichi.jp/articles/20211204/ddm/012/040/084000c https://mainichi.jp/articles/20211204/ddm/012/040/084000c Which seems from a major japanese newspaper if I'm not mistaken: https://en.wikipedia.org/wiki/Mainichi_Shimbun https://en.wikipedia.org/wiki/Mainichi_Shimbun