Yakuza Kiwami 2

Most of the information in this guide is from CyricZ on GameFAQs who has made plenty of other guides that I have used when I played all of the main series Yakuza games on PS4. Here is a link to their street boss guide. https://gamefaqs.gamespot.com/ps4/218734-yakuza-kiwami-2/faq...
(If you have a better farming spot for a group of enemies or if I messed up any details on this guide feel free to comment and I'll add it to this guide. Also, the bosses in Majima Saga don't count towards this achievement. Along with that just you must fight groups of enemies it cannot be just a singular enemy or if you manage to glitch out a group to where they'll only fight you one at a time.)

This sidequest can only begin in Chapter 5 once Sayama gets back up and walks around with you. You'll automatically begin a substory and the guy involved will tell you about street bosses. The way it works is that they will only appear after you've defeated a certain number of enemy groups. There are three types of enemy groups in the game: Delinquents, Thugs, and Yakuza, and for every five of each you beat, a new street boss will make himself known. After you've defeated 5 groups of enemies from a particular group you will receive an email from Komaki's Pupil telling you a new boss has appeared and will be marked on your map as a red skull with an arrow pointing down beneath it.

So, altogether, you'll have to fight a total of fifteen groups of each enemy type, both in Kamurocho and Sotenbori. So, here are some tips: First, equip the Charismatic Photo, which you can get from Substory #44 and later from the Sotenbori weapon shop in Chapter 6 or later. It makes enemies appear more frequently, but it's not absolutely necessary to do this.

Here are the enemy types you need to fight at each place and a general description of what they look like.

Kamurocho:
Delinquents - Theater Square and Nakamichi St. These groups will tend to wear more colorful clothing whether it be orange hoodies, varsity lettermen jackets, purple shirts with a rib cage on it, and usually, will most likely have a hat, headband or a bandanna.
Thugs - Champion's District, Park Boulevard, Hotel District. Usually will tend to wear stuff like a purple hoodie, orange and red jackets, or a somewhat flashy outfit. (This group seems the most common spawn out of the 3)
Yakuza - Around Millennium Tower, Pink St., Tenkaichi St. I suggest using the vending machines at the Shichifuku Parking Lot to shuffle the spawn, and then committing to the group if they show up near Bantam, or at the corner northeast of Millennium Tower. They look like basically every yakuza member you've fought in the main story of these games so they have fancier/flashier-looking suits than what some of the thugs wear. (Their spawn rate seems like the lowest of the three for me at least. I mostly farmed the east side of the millennium tower for a higher chance of spawns.)

Sotenbori:
Delinquents - South Shofukucho and the river footpaths. Usually will wear what the thugs wore in Kamurocho only difference is they look slightly more punk and will wear stuff like sunglasses.
Sotenbori Thugs - Shofukucho and the Cabaret Grand. For the most part, they look much like the thugs in Kamurocho.
Sotenbori Yakuza - West part of the city, from the Grand down to the parking lot in the southwest. I suggest going between the vending machines next to the Poppo on Shofukucho and the machines in the parking lot in the southwest and travel between the two. There are yakuza spawn points at either end. These yakuza members have the same style of looks as the ones in Kamurocho.

Email subject-Name of boss-requirement
Kamurocho:
On the Wrong Team - Fatal Fukishima - 5 Groups of Delinquents
Convenience Store Hunter - Saito - 10 Groups of Delinquents
The Lone Henchman - Samurai Mask - 15 Groups of Delinquents

Kamurocho K.O Knockout - Fujiki - 5 Groups of Thugs
Brawlectric Boogaloo - Muscleman Fujiki - 10 Groups of Thugs
The Ambush Specialist - Stealthy Kurosawa - 15 Groups of Thugs

A Dangerous Foe - Nutjob Natagiri - 5 Groups of Yakuza
Next-Gen Yakuza - Fire Karasawa - 10 Groups of Yakuza
To the Dragon of Dojima - Genso the God - 15 Groups of Yakuza

Sotenbori
Battle Junkie - Slayer Nagasawa - 5 Groups of Delinquents
The Breaker - Minegishi the Breaker - 10 Groups of Delinquents
A Formidable Foe - Iron Fist Sakai - 15 Groups of Delinquents

Test Your Skills - Nagafuchi the Skanda - 5 Groups of Thugs
The Weapon Hunter - Sakyo the Weapon Hunter - 10 Groups of Thugs
Rumble on the Bridge - Ukyo the Bridge Guard - 15 Groups of Thugs

The Deadly Assassin - Mysterious Assassin - 5 Groups of Yakuza
The Bloodletter - Tsujimoto the Bloodletter - 10 Groups of Yakuza
All That Glitters - Golden Kanamoto - 15 Groups of Yakuza

Your reward for defeating all these street bosses is the ability to purchase the Triple Quickstep ability and to use some of the bosses in Majima construction.