The Smell Road (腐臭の道) is a unique road, exclusively utilized by Onigiri who invented it.
Chiefly, the Smell Road is concerned with distorting the opponent's senses and creating illusions. Onigiri accomplishes this through extreme perspiration, the smell of which the opponent inhales and can cause many different reactions which range from hallucination, to mood suggestion, to poisoning. Secondarily, the sweat Onigiri secretes can slick the road and cause difficulty for any rider.
It is possible that the Smell Road is useful only against female opponents, as Onigiri finds difficulty in accessing his abilities when he lacks the proper motivation (sexual excitement). Recently however, Onigiri seems capable of circumventing this weakness by reimagining any male opponent he might face as a naked female.
Mucus - Onigiri releases mucus from his his nose and makes any projectiles slip (such as Nike's Shard Bullets) of his mucus.
Smell Road: Fog Assassin - First demonstrated against Freyja in Kogarasumaru's battle against Sleipnir. With this trick, Onigiri is able to fill an opponent's lungs with poisonous gas. It is unique in the sense that it has no effect unless combined with a trick that causes extreme shockwaves, like Kazu and Agito's Grand Fang Firebird. When activated by these shockwaves, the poison inside the opponent's lungs is agitated and causes them to lose consciousness.
Imagine - Sweats profusely, inducing an illusion that lowers his target's inhibitions and makes them open to mental suggestion. Used to defeat Mimasaka Ryo during the Behemoth Match. In chapter 289 he shows that he can use the illusions on himself to make male opponents appear female so he can fight them at maximum power.
Sweat - The sweat Onigiri secretes can also be used to slick the ground and be a road hazard to any rider. He can use this to cause projectiles such as Nike's debris attack to simply slide off his body. And his sweat has been shown to nullify the vibrations created by the Gem Regalia preventing paralysis.
Titty Twister Heartbreak Show - A screw shaped attack which is apparently pretty powerful when used right. By the name OG's positioning of Nike during its use it can be assumed that he grabs the enemies nipples as well.
Delusion Max - The usage of his Smell Road to its highest potential via combining his "Ero" power with nitrogen. It brings his battle level to 360 when used. Onigiri's powerful bodily odor is created by a nitrogen compound found in his sweat. Speculation has been made that the delivery system of such quantities of nitrogen to his sweat is similar to the Sonia roads. It also tampers with brain functions. The most notable thing to keep in mind is that it is an essential compound in making gunpowder and possesses enough potential energy to create an explosion when ignited.
Final Ero-Power Release - By using Delusion Max to what seems its very highest he releases a vast amount of sweat. However this seems to be Kamikaze in nature due to him setting of an explosion right after using the nitrogen in the sweat. Due to the nature of the scene to which it was used in 316 it seems to eliminate his ability to use his Eros Power making him both weakened and defenseless.
Organic Nitrogen - Onigiri is able to use the nitrogen in his body to create explosions and assist users of the Flame Road.