Worth mentioning, as someone has for Kakao below, the LINE app has a magnitude or two or three more features than Signal. Beyond chat, the app handles payments including retail via QR, effectively has Instagram and TikTok built in, has an entire news section, and much more.
Heck, LINE the company even has permanent and pop-up merchandise stores in downtown Tokyo (Harajuku) and their own MVNO mobile carrier called LINE Mobile.
Now that said, I loathe LINE, the app. The UX is poor and the app is bloated behind belief. Only use it effectively out of necessity as someone living in Japan. The only alternative communications channel even remotely close in usage is probably Instagram chat.
Can confirm, can get just about anything unscented in Japan. Thankfully likely due to the general societal norm of not having a strong smell wafting about oneself. Though not all abide, most do.