The PV is... everything! I watched it and I was surprised when I suddenly got choked on my feeling. It has that nostalgic aura that - you know - somehow I ended up reminiscing all of my moments with Arashi. The feeling when I first got hooked up with them - the joy and all the fangirls moments, be it good or bad. Everything just came back to me and I felt tears rolling down.
All of Arashi's arigatou songs has that gratitude and how thankful they are to their fans. Starting with Sketch, then 5x10 and now 5x20. Perhaps, it has something to do with the coming hiatus, but the song really went straight to my heart. It's like their telling the fans not to worry and you can really feel how grateful Arashi is to their fans and how they treasure their 20 years together.
I think, 5x20 is not only for the fans, but also for each of them. To tell each of the members how grateful they are towards each other. Each moments, the terrible and the good moments are a treasure for them because they have each other.