In Senran Kagura: Peach Beach Splash, at the end of each Arc that divide the game's story (except the Climax Arc, for which the Final Splash serve in sorts as its boss battle through separated into a separate arc), the player has to face a certain boss battle with special mechanics. They come in the number of 5 battles, for 6 bosses in total.
Hanzō Arc: Gropety Grope Machine[]
Controlled and given by Kiriya as a "gift" after he seemingly restrained Daidōji, the Gropety Grope Machine is Hanzō Arc's boss. It is a floating machine with a face, sealed eyes, big hands, propellers and thrusters on its sides, and two cannons on its back. Kiriya is holding to its side.
It will attempt to get to Daidōji from 200 meters of her, and the Hanzō team have to prevent it from eventually sexually harassing their senior. The machine's weakness is its nose, which is the only part capable of being damaged, while water is ineffective on the rest. Note that the machine is accompanied by lesser enemies.
When it is harmed, the machine will hide its nose for a little time, and will throw projectiles if a character gets too close of it. If the player successfully vanquish it, it will explode while Kiriya jumps away, ending the mission. Else, if the player leave it get to Daidōji, it will seemingly grope her, resulting in a failure.
Crimson Squad Arc: Lickety Lick Machine[]
Controlled by Kiriya after he seemingly captured Rin, the Lickety Lick Machine is the Crimson Squad equivalent of the Gropety Grope Machine. It is flying metallic duck with a propeller on the head, giant wheels inside the body, and wings on which stands Kiriya. A long tongue is wriggling from its "beak".
Like the Gropety Grope Machine, it will attempt to get to Rin from 200 meters away, leaving the Crimson Squad no other choice than destroying it to prevent it from licking their former teacher. The machine's sensitive point is the tongue, that wriggles, making it hard to aim. The rest of the machine is invulnerable to water. Lesser foes accompany the machine..
The machine can retreat when harmed, and might try to slap with its tongue or to ram when its opponents get near, striking the unlucky foe with its giant wheels. It also can charge projectiles from its wheels. It can also throws drool from its tongue as projectile. When it reaches Rin, it will lick her hardly, while it will explode if successfully vanquished, with Kiriya jumping away.
Gessen Arc: Ms. R and Mr. K / Jet-R and Jet-K[]
As the final challenge of the PBS tournament, Kiriya and Rin fight the Gessen team using two humanoid robots, Jet-R and Jet-K.
Both robots are flying above the ground, have a chest face, mounted weapons as arms, and surfboards as feet. If they get damaged enough, they can be downed, and their drivers about to fall, allowing the player to really damage them. If they are vanquished, they will explode and send their driver away.
Jet-R seems to be equipped with a water crossbow and a water cannon, while Jet-K has a water shotgun instead of the crossbow. Jet-K doesn't fall on the ground unlike Jet-R.
Hebijo Arc: Ryōna the Elegant[]
Unlike the others, Hebijo has not to deal with the tournament animators' strange plans, but rather with their own teammate, Ryōna, who found another enbiggering potion, and became giant. This is the third time this happens. She is standing in one of the Onsen's pools covered in soap.
The player has to clean up all the soap from her, who is not a threat by herself as she doesn't attack the player. The main threat is the lesser enemies that appear on the floor above the pool.
Once the player finishes cleaning her, she shrinks to her normal side again.
Final Splash : Heaven's Casket[]
Unsatisfied with the girls' performance through moved by their enthusiasm, Meiun orders Kiriya and Rin to lead them to a remote island for the Final Splash.
Ryōki stands as the final boss, again, and acts as a DJ for the deadly Heavy's Casket, a big musical machine which the appearance reminds of herself, with coffin-shaped speakers and spotlights, and a halo in its back. The weather is dark.
Heaven's Casket is the most dangerous machine of the game, as it is capable of doing spin attacks that strip if no insta-KO the ones that get caught in, but also uses sound waves as projectiles, and the more it is damaged the more it becomes dangerous, capable of sending glowing balls or emitting lasers. The use of shield cards is highly recommended.
The way of defeating it is similar to Jet. R and Jet. K : The player has to damage it enough to get it downed, which will allow the player to deal damage during a short amount of time. When the machine gets defeated, it will explode and send Ryōki in the air, stripping her in the process, through restoring a clear and sunny weather.