The second teaser used ウソ for uso (that is katakana, which is used for lone words and as a stylistic choice void of inherit meaning like with kanji), which is mostly viewed to mean “lie” 嘘 to fit the theme/make sense, but is also a neat reference to “otter” which is 川獺 or “kawauso” in Japanese.
The third teaser used 河 for river, rather than the commonly used 川 (that you can see in the kanji for otter or “river otter” as well). 河 is mainly used to represent large foreign rivers, particularly 黄河 or “Kouga”, the Yellow River, in China.
Additionally, I found out from this blog that because of this connotation 河 is actually more used to represent large scale objects and matters rather than rivers, like 銀河 for galaxy, 氷河 for glacier or 河馬 for hippopotamus.
It’s interesting to see how they’re clearly referencing otters, but not with the words you’d commonly use. I also get the feeling that we’re in for something grand.