Seong-hui has long, dyed lilac hair. She wears a leather jacket and black miniskirt, a pair of leather gloves, and a pair of heels. She has several ear piercings, including silver hoops and an inner-ear bar. On her necklace she wears a spider pendant, likely meant as a nod to the Geomijul's "spider web" of electrical wires.
When she first appears, she shows very flirtatious behaviour, especially towards Ichiban Kasuga. After being revealed as the Geomijul's leader, however, she behaves much more seriously, almost showing a ruthless side to herself by aiming a gun at Kasuga's throat while interrogating him.
Later, after more open co-operation between groups begins, she behaves more jovial, though apparently shows some restraint.
Seong-hui came to Japan as a child with her mother and some other fellow Koreans who resides in Yokohama. She was originally a part of the Jingweon Mafia, but later defected and formed Geomijul, a syndicate that consists of Jingweon exponents who are abandoned and refused re-entry.
Yakuza: Like a Dragon: 2019
She first appears outside of the Geomijul HQ, wearing dark sunglasses to hide her face. She leads Kasuga and his party within Geomijul territory, all the while "flirting" with the ex-yakuza. Upon them entering the building, however, she disappears from view.
Once Joon-gi Han shows the group the extensive counterfeiting operation the Geomijul is partaking in, she reappears and is named as the organization's leader. After a brief back-and-forth, she draws a pistol and aims it at Kasuga's chin, taking the counterfeit bill he had in his pocket after being dumped in Ijincho. Kasuga manages to convince her that he knows nothing about the bill, leading her to relax slightly.
However, she immediately points the gun at Nanba, accusing him of spying on the Geomijul since his arrival in Yokohama six months earlier. Nanba then confesses, after pressure and a pistol-whipping from Seong-hui, that he was only traveling with Kasuga in an attempt to find his brother, who had been investigating the counterfeiting in Ijincho before his disappearance. Seong-hui shocks him with a taser and orders her men to take Nanba away, before Kasuga stops her and demands his release. Angrily, she orders Joon-gi and the other Geomijul to attack them. Eventually, however, she reluctantly relents and allows Kasuga to flee, but warning him that this was only the beginning.
After Kasuga's escape, she convened a meeting of the Ijin Three - herself, Ryuhei Hoshino and Tianyou Zhao - regarding Nanba's knowledge of the counterfeiting. Eventually, they agreed that Nanba had to be silenced, leading to Zhao sending Liumang assassins after him. Though Kasuga and his friends saved Nanba's life, he had already divulged the information he had to Bleach Japan, and openly assisted their attempted raid on the Geomijul. After Kasuga, Adachi and Saeko managed to slip past the Bleach Japan rioters, Seong-hui and Joon-gi asked for their help. The Geomijul would destroy their counterfeiting operation with a fire, while Kasuga and his friends stopped anyone from interfering.
After Akira Mabuchi's Omi Alliance-backed coup of the Liumang failed, Zhao resigned as the head of the group, and told Kasuga he intended to name Seong-hui as his successor, thereby merging the weakened Geomijul with the remnants of the Liumang still loyal to Zhao. Later, she reappears with Hoshino, Kasuga and Zhao in a Chinese restaurant, where the four discuss how to openly challenge Ryo Aoki's growing influence.
Later, Kazuma Kiryu (acting anonymously) asked Seong-hui and the Geomijul to look into Aoki's potential plans to send an assassin after Jo Sawashiro, after he surrendered to police. Using the Geomijul's rebuilt surveillance systems, they managed to find Mirror Face and Reiji Ishioda in Ijincho, apparently preparing to kill Sawashiro. During this task, she also looked into Kiryu, discovering his identity and the reasons as to why he was choosing to remain anonymous, something she almost accidentally divulges to Kasuga.
After the joint funeral for Masumi Arakawa and Aoki, Seong-hui is among the friends who intercept Kasuga, Nanba and Saeko outside the funeral home, wanting to know if Kasuga intended to leave Ijincho. She admitted that she didn't know Kasuga cared about his friends in Yokohama after Saeko repeated what he'd said inside.
- She admits that she has a large appetite, as she describes her stomach as "a bottomless pit."
- She is also very particular about her coffee, as told by Joon-gi.
- Like Hamako, her outfit is available for both Saeko and Eri Kamataki to wear as a job uniform via DLC.
- She despises rats and cockroaches, to the point that Joon-gi claims that Yokohoma would "drown in a sea of flames" if she spotted the pests in Geomijul.
- The given height of 170 cm (5′ 7″) is based on the character model's scaling factor within the game's data. For Dragon Engine games, this method is believed to be very accurate (±1 cm). However, this is intended as an estimate, not a substitute for an official statistic.
- Yakuza: Like a Dragon (Ryu ga Gotoku Studio, PC, November 2020) - .JSON File - "character_model_model_data.json"
- Table Talk scene with Joon-gi, unlocked by ordering Wette House Coffee at Wette Kitchen.