Well, I think any Asian language is difficult to learn. What makes Japanese the "easiest" out of the rest?
P.S if anyone has any other subjects that they consider easy H1s (not just languages) please contribute 
To be honest I think Latin is much easier than Ancient Greek. Contrary to what notveryasian says, I think it works the other way. If you really understand Ancient Greek, then Latin (and I hate to say this phrase) seems piss easy. After all, Latin basically takes all of its grammar from Ancient Greek, but it doesn't take
all the Ancient Greek grammar, if that makes sense. For example, there is no optative in Latin nor is there a medio-passive voice, to name twotwo instances. There is also an Aorist tense in Greek, which is similar to French passé composé. Also, there are no real regular verbs in Ancient Greek and verb tenses are derived through root and consonantal vowel changes rather than the common -o -ere/ire -ivi/ii - itus/tus endings. In my opinion, the Greek verb system works much better even though it is more complicated. So for example the principle parts of the word 'to carry/bear' (from which the latin word fero is derived):
phero, oiso,enenkon/enenka,enenoka,enenegmai,enekthen, enekhthesomai
but then the verb 'I think': oiomai, oiyesomai, oiyethen
I actually find that Greek is a much more rewarding and beautiful language than Latin. Latin seems rather boring after Greek...I'm sure you will really enjoy it!
That said, definitely not a subject to do if you want a certain H1 without doing much work. Class average for translation tests last year was about 6/20 (but it may just have been my lecturer who liked to give beginners Greek passages from Aristotle's Metaphysics, which was actually really great but just really difficult). But then there were only about 7 people in the class, and some of them weren't very hard-working at all. If you want to do really well, you need to knuckle down big time. It worked for me, but it depends how good you are at unseen translation and contextual semantics.