The soldiers with daggers can be a real pain to defeat, largely because they constantly block and can deal you some serious damage on the counter-attack.
You should find a combo that breaks their block and their armor - everyone has one which will cause them to stagger and allow you to follow up. With Ryu you can use YYYYXX, YYXXX or lunar YYXXX. With Kasumi try YYYXX. These should break their guard and allow you to finish off.
Karma Points are used to spend on a specific character to improve them with unlockables and extra items. The Karma Points can only be earned by playing as that specific character, so if you play as Kasumi, you will only earn Karma Points to use on Kasumi.
When you start a new game in Ninja Gaiden 3:Razor's Edge, you can elect to maintain all of your levels and weapons. To do this, select the option to use your Base data when confirming to start a new game.
The battle against the two spider tanks on Day 7 is hard enough normally, but on Ultimate Ninja mode, it may leave your controllers smashed and broken on the floor!
The mass of rockets that are sent your way are likely to leave you frustrated. The easiest way to combat the tanks is to use True Inferno, as this will put all the spider's legs into Critical mode, allowing you to finish them off normally.
You may have to restart the level so that you can plan for the Inferno attack.