Don't forget to buy food and drinks in advance if you need them: train stations do not always have shops, while onboard cafés are not always available and often very expensive.
Since the journey between Koshigaya and Shinjuku is relatively short, you can consider carpooling or bus as alternative ways of transport with cheapest prices and similar duration.
In which stations can you take the train to Shinjuku and where will you arrive?
Trains leave Koshigaya from KOSHIGAYA-LAKETOWN or KOSHIGAYA and arrive at SHINJUKU(JR), SHINJUKU-SANCHOME or SHINJUKU-NISHIGUCHI.
How long will it take you from Koshigaya to Shinjuku by train and when do the trains leave?
The first train to Shinjuku leaves at 06:12, whereas the last one at 18:12. On average, the journey lasts 1 hour and 1 minute, but with the fastest connections you will be in Shinjuku in 49 minutes.