There aren't any rights to translate unless you get legit permission from the original author to do so and post his work elsewhere on the web. After all, if such permission is not given, then its infringing the rights of the original author.
An interesting choice of translation for 覇界王 / Hakai Ou there at the end of the first chapter. Overlord doesn't work for it, seeing lit. would King of Destruction, which is a play on GaoGaiGar's title as King of Braves.
Fun fact; The title of this page is wrong. The chapters here are from the first four books Red Fang/Akai Kiba, while Blue Sonnet is the seventh part of the series, which has no page translated chapters here.