Very poor airline indeed and their collective weight limit of 7kg max is a disgrace too. Unless you're going away to Japan for a 1 or 2 days there's no way that anyone can remain within that low threshold. From my observations it looked like everyone was caught out by this ridiculous restriction and had to fork out.
This airline is a scam (like many LCCs in Asia, but probably the worst). Their booking system doesn't confirm passenger names at the time of bookings, and their email "confirmation" is too small for most Western names (Japanese names are usually three characters). My name was (apparently) truncated during the booking process, but due to the shortcomings in the reservation system (which I now think are intentional) there was no way to know until I turned up to check in, at which point I was told that my ticket was invalid and it was too late to do anything about it, and left stranded in Tokyo with only a partial refund. It cost me three days and hundreds of dollars to fly through the Philippines instead, as all flights were full, it being Chinese New Year.
Check-in staff admitted that there was no way for me to know since the name is never confirmed (at payment or in the email confirmation) and said that customers are denied boarding over this "problem" regularly, and they seemed surprised when I refused to purchase a new, expensive fare on the spot.
It appears that the airline overbooks and refuses boarding to people over this regularly. In all fairness most LCCs make most of their profit (if they make any at all) from customers who never fly, but refusing boarding to passengers who have paid for their fares and turn up at the airport to fly takes the LCC business model to a new low.