Having sex with your party members increases their MP pool, so eventually you will have a large enough MP pool to make it through with the abilities he mentioned. For example, I had about 1200 MP with 5 girls in the partywhat have that to do with skill not that its me that fight or say how they have to fight so i need skill for something Enemy hit you and drain your MP from level 35 on 2-3 Hits are enough and you are back in the city and the teleporting dont help as i try that every time i reach the next level the enemy direct hit me before i can hit Esc to use the next teleport in the first level it work but again from 35+ the 2-3 hits in that moment when you spawn on the level are enough to send you back to the City
Also, there are active abilities that can kill enemies or prevent damage without using MP. i.e. Riley's Explosives, Rachel's Gun, Alexia's Guard, etc....