I am a huge fan of Boueibu (Earth Defense Club LOVE!) and started using Otsukai in the hopes of completing my Boueibu LOVE collection! My most wanted item is the milk bottle of the Defense Club from the 2016 Oedo Onsen Collaboration and the full set of Io Naruko's Birthday Festival Badges from the Chara in 2016.
Aside from Io Naruko from Boueibu, I'm also interested in merchandise of Ryuu Zaou (also from Boueibu), Yamato Nikaidou (IDOLiSH7), Eijirou Kirishima (My Hero Academia), and can badges of Shirai Yusuke (the seiyuu of Io and Yamato).
I'm generally pretty good at finding the merchandise I want. All of my requests are for the rarer items I can't find. So far, Otsukai has helped me to get a few of my most wanted Boueibu items. Hopefully, it can help me find the rest!