To get this you have to get through 9 levels for Pamu. Each level has up to 4 goals you must complete to reach the next level. The possible goals are, reaching a specific number of hearts, reaching a specific amount of money, giving specific gifts, taking the girls on dates, reaching a specific level in your hobbies/jobs.
The goals for Pamu are
Level 1 Adversary
5,000 Hearts
Level 40 Buff
Level 2 Nuisance
50,000 Hearts
Level 42 Badass
Level 3 Frenemy
512,500 Hearts
2 Diamonds
5,000 Hand Lotion
Level 44 Suave
Level 4 Acquaintance
5,253,125 Hearts
Level 46 Angst
5,000 Drink
Level 5 Friendzoned
Level 6 Awkward Besties
Level 7 Crush
Level 8 Sweetheart
Level 9 Girlfriend