Like a Dragon: Infinite Wealth

You'll find the Ounabara Vocational School in the southwest region of Honolulu, on Harbor Street, where you'll be able to initiate the 'Playing With Fire' substory. The first exam is free, but subsequent exams will cost you. There are 21 certificates to earn in total, so you need only complete a few exams for this. However, it's worth completing them all, as they help boost Kasuga's Personality traits. Completing ten exams won't make Ikari too happy, but it will bag you this achievement.