Sorry to disappoint but Soju is haram. Anything contains more than 0.5% alcohol is haram to be consumed/eaten/drunk. As I looked on Google and Wikipedia, Soju contains at least 16.5% alcohol.
From Wikipedia (View the full Wikipedia article here):
Soju (/ˈsoʊdʒuː/; from Korean: 소주; 燒酒 [so.dʑu]) is a clear, colorless distilled alcoholic beverage of Korean origin.13 It is usually consumed neat, and its alcohol content varies from about 16.8% to 53% alcohol by volume (ABV).[4][5] Most brands of soju are made in South Korea. While soju is traditionally made from the grains of rice, wheat, or barley, modern producers often replace rice with other starches, such as potato and sweet potato. This liquor features in the drinking culture of Korea.
From Islam Web (View the discussion here in English):
The fact that a given beverage contains an amount of 0.5% or the like of alcohol does not entail deeming its consumption unlawful as long as there is no effect of the alcohol upon consumption of the beverage and it does not intoxicate in large quantities.
A fatwa from Mufti Wilayah Persekutuan Malaysia goes into details about this issue (English version in Google Translate here | Original version in Malay here):
- While alcohol obtained not through the process of making wine is not najis, but it is haram in its original form. In other words, it cannot be eaten in its original form (ethanol) because it is poisonous and can kill.
- Soft drinks are processed / generated not with the intent to producing wine and has an alcohol level below 1% v / v is a must (be) taken .
- While soft drinks made with the same intention and manner as the process of making wine , whether containing much or little alcohol or distilled alcohol are haram (illegal) to drink .
- Foods or beverages that contain alcohol naturally such as fruits, nuts or grains and their extracts, or the alcohol contained that occurs incidentally during the process of making food or beverages are not najis and should (can) be eaten.
- Foods or beverages containing flavorings or colorings containing alcohol or ethanol for stabilization purposes is halal if the alcohol is not produced from the wine manufacturing process and the quantity of alcohol in the final product is not intoxicating and the alcohol content does not exceed 0.5%.
- Medicines and fragrances that contain alcohol as a solvent are not najis and are permissible if the alcohol is not taken through the process of making wine.