The further into Judgment you get, the more you’ll probably struggle unless you’ve powered up Yagami by unlocking skills.
There are a myriad of skills to unlock in Judgment, spread across three categories. Some of them boost your skills in combat, while others provide benefits outside of combat, such as making tailing people or picking locks easier. You don’t need to unlock many of them as you make your way through Judgment, but it’s safe to say that you might eventually find yourself struggling in battle if you don’t upgrade things like your maximum health and attack strength. To do that you’re going to need to amass SP, with which you unlock skills.
You gain SP for nearly everything you do in Judgment, albeit generally in small quantities. You gain it for buying and eating food at restaurants, for example, and carefully selecting the right dialogue choices. You also gain it for defeating thugs and Yakuza that you encounter around Kamurocho – they harder they are, the more you get. One of the most lucrative sources of SP is becoming friends with shop owners. Spend 7,000 Yen in a shop and you’ll become friends with the clerk. Not only will you get a record to play back at your office, but you’ll also gain a 500 SP bonus.
Unless you’re desperate to gain SP in order to unlock a specific skill, however, you’re better off just playing through the game’s story. You’ll generally earn 100-200 SP for every objective you complete, and it adds up really fast. As you play through the game’s story, chances are you’ll also complete many of the game’s milestones, which award decent amounts of SP. Bring up your phone and enter the Kamurogo app if you want to see what those milestones are and steer yourself towards them.