Via tokyohive:

Korean "beastly idols" 2PM performed at the "12th Tokyo Girls Collection 2011 Spring/Summer", the largest fashion festival in Japan, which was held at the Yoyogi National Gymnasium in Tokyo. As reported the other day, the six members were excited to perform at the fashion show, and with 23,000 people in the audience, along with 720 journalists and even more viewers on their YouTube live channel, they sure had plenty of reasons to look forward for their stage. The reception was great, which is no surprise when considering they were performing in front of a crowd full of thousands of excited girls, and their amazing performance could have converted any skeptic into a fangirl. Member Nichkhun commented in perfect Japanese, "Being able to be here today and standing on this stage makes me really happy." Meanwhile,�Taecyeon was taken aback by all the beautiful girls. "We heard that all the stylish girls from Japan gathered here at this event and it really seems to be true," he laughed, "I'm quite nervous now." Nichkhun ended their little comment section and appealed to the audience, "After this, we are going to be more active in Japan and we hope that you will support us." The group performed a total of four songs: "Heartbeat", "Again & Again", "Without U", and "I'll Be Back". Source: Model Press

If you want to take a look at the gallery of pictures from the event, it's in the tokyohive article.