Leeteuk once said that his ideal type is some mix of SNSD Yoona, Taeyeon and Seohyun. Fans noticed that Leeteuk treated Seohyun differently from the others as Seohyun is the type of girl that easily gets shy. It is revealed that Leeteuk gave Seohyun a nickname 'Princess Angel Maknae'. 

On Challenge Golden Ladder, Leeteuk keeps calling Seohyun, an angel. When Sooyoung was talking, Leeteuk suddenly appeared with a bouquet of flowers and end up giving to Seohyun. There's a moment when a boy keeps holding Seohyun's hand as part of his show but Leeteuk couldn't stop glaring at the boy.

On Kiss The Radio, SNSD's members revealed that Leeteuk always had love for Seohyun. According to Tiffany, Leeteuk liked the maknae since before debut.  He then defends Seohyun by saying that she is always pretty. Yoona then added how Leeteuk always showed care for Seohyun whenever he called. He was happy when Seohyun answered that she didn't have an ideal type. After the show ends, the members were about to take pictures. Leeteuk couldn't stand straight as he felt shy standing next to Seohyun. Thus, Yoona had to stand between them. After Seohyun had graduated, Leeteuk asked what she wants as a gift which she replied she only want a machine to cook goguma.

On 100 Song Challenge, Leeteuk keeps calling Seohyun, our Seohyun-shi which caused the mc to step up.

On JBJ Talk Show, Leeteuk is over-protective of SNSD's Seohyun. He said that Seohyun must stay the way she is (as single). If anyone wants to meet Seohyun, that person has to pass through him first. He was extremely excited when he is choosen as the second best ideal type in SM. During dinner, after Seohyun feed Changmin who was busy cooking, Leeteuk showed his jealousy by shouting 'Noo~'.

Kyuhyun once said that he likes girl with long hair and have beautiful forehead. For me, everytime celebrities revealed their ideal type, they always reminds me of Seohyun as she is extremely perfect. Kyuhyun has the same habit as Seohyun. Both of them like to take public transport. Furthermore, the two maknae also played the same role in their group (as the third main vocalist) (explain how to visit SMTown page)

During SMTown Good Day, Kyuhyun and Seohyun were caught sharing earphones together to practice for their duet concert. Kyuhyun jokingly admitted that they are SM unofficial couple. Seohyun then asked the other oppas to take picture together. But Kyuhyun didn't satisfied and took another picture of him and Seohyun. While performing 'Call Me With All My Heart', they inserted some skinship such as holding hands. Kyuhyun touched Seohyun's cheeks and her hair while Seohyun rested her head on Kyuhyun's shoulder. Seohyun told Yonghwa that she couldn't stare at her partner while singing. But during the concert, both Seohyun and Kyuhyun happily staring at each other.

During WGM YongSeo, Seohyun bragged about her skinship with Kyuhyun to Yonghwa and caused Yonghwa to explode into jealousy 

During The Making Of Seoul MV, Kyuhyun was asked if he was cold filming during winter. He showed care for Seohyun when he said that, compared to Seohyun who was only wearing a skirt, that type of cold was worth to be tolerated with. The two were playing happily while filming for the mv.

During Super Junior Interview, Kyuhyun praises that Seohyun is very polite to her unnies. He wished that Seohyun will treat Super Junior oppas the same.

On Radio Star with 2am, when Jinwoon revealed that Seohyun had came to his birthday party and sent him a congratulation message, Kyuhyun seems shocked,

At MAMA Award 2011, Kyuhyun was standing behind Seohyun. He called 'Seohyun-naaa' and said something to her. After that, he then smiled shyly.

During KMW Goggle, when Kyuhyun was singing his line.. he saw that Changmin was handing Keroro to Seohyun. His eyes couldn't stop staring at both of them. When everyone  was all on stage for the finale, Kyuhyun was standing near Seohyun all the time. Kyuhyun then grabbed Seohyun's hand when it's time to greet the audience.

When SUJU & SNSD were dancing to 'Move Like Jaggers', Seohyun and Kyuhyun had some skinship. After the performance ended, Kyuhyun patted on Seohyun's shoulder

In Strong Heart ep 140, Kyuhyun accidentally admitted that he is jealous of Eunhyuk and Seohyun. During Seohyun's birthday party, Eunhyuk became the first person to arrive and sat together with Seohyun. But later, this part was completely edited out. Maybe because SM didn't want any scandal between the two group maknae.

In his twitter, Kyuhyun tweets about typhoon which Seohyun had sent to people around her.

During Kiss The Radio, Ryeowook receives text from Seohyun that advice people to watch out for typhoon. Suddenly, Sungmin became sulky as he felt being left out. Ryeowook forward Seohyun's messages and thanked Seohyun for her consideration.

After the SMTown in Seoul finished, Ryeowook was seen splashing water to Seohyun.

In his twitter, Eunhyuk twitted that Seohyun had sent him an invitation to her birthday party.

At Seohyun's birthday party, Eunhyuk was the first one to arrive. The two then awkwardly had a toast together.

During JBJ Talk Show, when Seohyun was asked about her ideal type in SM, Yunho noticed that Leeteuk, Changmin and Eunhyuk felt nervous and drank water at the same time. During dinner, after Seohyun feed Changmin, Eunhyuk felt a little jealous and wanted to be feed to. Seohyun ended up feeding him but half way.

During the ending of SMTown In Seoul, Yesung asked Seohyun to walk to the front of the stage with him and the other SNSD members. He grabbed Seohyun's hand and linked it into his arm.