Let me paint you a picture...
Umi and Hino have both grown up and are dating because, despite their differing professions they still make time to spend time each other. Eventually, Umi starts thinking about marriage and tries to think up a way to propose to her Ra-Man... so she goes to a jeweler and pays the jeweler with all her science money, (She got it from solving the energy crisis with lizards or some shit I dunno) to craft the perfect Item.
Eventually It is finished and she proposes to Hino with.......
A TANK TOP CRAFTED FROM FUCKING GOLD AND ADORNED WITH JEWELS!
(Un)surprisingly he was able to wear it all the time despite the fact that it was like 60% diamond but, this is Tank Top Chad we're talking about.