-Estimated achievement difficulty: 2/10
-Offline: 13
-Online: 0
-Approximate amount of time to 1000: 15+ hours
-Minimum number of playthroughs needed: 6
-Number of missable achievements: None
-Do cheat codes disable achievements?: No cheats
-Does difficulty affect achievements?: No
-Glitchy achievements: No
-Unobtainable achievements: No
-Extra equipment needed?: Japanese Console
This game is pretty mindless, but you'll divulge much time and frustration in collecting all the cards for a character, as it is practically luck based. The mindless time you'll put into this warrants the 2/10 achievement difficulty.
Introduction:
If you've ever played Gradius, you've already played this game. It's essentially a Gradius clone featuring barely clothed women (and one dude) operating the ships. The game's weapons and upgrades are just like Gradius, and in fact some of the levels and attack patterns are like it too. Anyways, the achievements are all very simple, and you'll have 700+ in less than 5 hours, it's the rest that will take a lengthy and somewhat uncertain amount of hours.
Step #1- Six Playthroughs
Playing through the game in G-Mode with each character will net you 600, touching the angels in the character select screen will net you another 100. There are unlimited continues so there is no difficulty in this whatsoever.
Step #2- Weapon/Illustration Cards
Now you'll have to work on getting the cards for ONE character. Use the method detailed in the achievement guide to collect all the cards for one character. The more cards you get, the less often you get new ones, so you could be playing hours and hours for that last card. Collecting all the cards will net 200. While on your way, you will have played 573 minutes, netting 100 total.
Conclusion
You can breeze through the first 700-800 with no effort in just a few short hours. If you have the patience, you can get the full 1000. Time consuming, but effortless.