Someone hacked your account or knows your account password.
You can recover your account if you stake a bitcoin address and make a sign message to prove that you own that account.
check this
https://bitcointalk.org/index.php?topic=497545.0If you don't stake your bitcoin address anywhere here in forum it would be hard to recover your account back.
Thank you.
Another interesting note. While searching the spam section of my mail I came upon this. Its from 22/3.
Thank you for registering to Zaif Exchange.
Please register your personal information after setting up your password from the URL below.
https://zaif.jp/register/bfe8d75a-512b-4b4f-9cef-377ea122a4f3The above URL will be invalid after 24 hours from issuing
また、既に上記URLよりパスワードを設定をおこなった場合も、URLは無効となります。
If the link becomes invalid, please do registration procedure again.
If you have any concern, please contact to Support.
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Cryptocurrency exchange Zaif Exchange
https://zaif.jp/registration number: Kinki Local Finance Bureau No.00002
The plot. The plot thickens.