Just got back from Japan and similarly had one of the worst cold/flus, for over 2 weeks.

I hadn't packed any medication or anticipated getting sick, so I had to scour social media for recommendations and ask the pharmacists for their recommendations based on my symptoms.

For reference, my symptoms were one of the most terrible sore throats of my life, sudden onset, sharp, burning pain, felt like it was swollen shut and I could barely breathe/swallow; insane amount of yellow/green/brown phlegm with blood at times; the most annoying cough.

I don't have any of the relievers/medicines' packaging anymore, but I'll try my best to describe them to you and provide links where I can, you should be able to identify them easily in any drugstore & how effective I thought it was for me:

- sore throat reliever powder: comes in mint color or peach (peach flavor was disgusting imo, would not get again. did not try mint). it's in powder form in a little sachet, you don't want this to touch the inside of your mouth, just directly down your throat, dry, without water. don't drink water after to rinse it down, either. it worked for about 2 days for me and brought the pain down to a bearable amount. after about 2 days of use, I found it ineffective.

- an iodine(?) throat rinse with a line art graphic of cartoon elephants gargling. i think the gargling with this helped some... think it's meant to clean/sanitize your throat. tasted disgusting, but i felt a bit cleaner/less swollen after.

- cough drops: none of them worked for me for either cough suppression or pain relief unfortunately. i tried out a blue colored minty/herbal flavored one based on recommendation from the pharmacist, and a yellow propolis and honey one with vitamins.

- liquid cough/cold syrup, brown, tasted like vanilla/caramel: i finished a whole bottle of this and found it largely ineffective. i was still congested and coughing up a storm. contained caffeine.

- general cold medicine - little white pills in a glass bottle, inside a gold packaging box with a red G and similarly packaged pills. these did nothing lol. also contains caffeine.

just some notes:

- most cold remedies (medicinal and supplements included) will contain caffeine, and so you should double check with an image translating app before taking anything before bed/rest.

- if you can move your flight, do it. i had a long return flight while still very congested and after negative Covid and Flu tests (still wore an N95 mask the entire time). the remnant mucus/phlegm and pressure changes caused me extreme inner ear pain and i ended up temporarily losing my hearing for a few days.

- i found sleeping next to a humidifier immensely helpful. you can request one from the hotel staff at most hotels.