Based on reviews on Happy Cow I went to Green Earth restaurant. It is relatively easy to find because it is on a road parallel to "Mido-suji" which is one of the main roads in central Osaka. There's a prominent Happy Cow sticker on the door, which was very assuring.
The restaurant isn't exactly cosy and looks more like a cheap office canteen than a restaurant. The menu is available in English and the waitress showed pictures of each dish on her phone. Great service!
I ordered the "Soy BBQ with rice bowl" and it was brought to me swiftly. The soy was a brown substance which didn't really have a joy like bite, but it was okay. The ingredients didn't taste like top quality ingredients, but then again the prices are very low. The rice bowl was a mere 650 yen, so one cannot expect top quality at that price. Instead the Green Earth restaurant offers decent vegan food at a very decent price.
As reported before: the restaurant is open daily for lunch. It is only open on Friday evening for dinner.
Cons: not the best in town