You might find Basara a good read, it's a romantic, historical manga with a similar war back drop.
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He's Dedicated to Roses is similar.
Any online manga source such as MangaFox.
There is a manga called Koko ni iru yo
mangafox.com sometimes does.
There isn't any Bisexual manga as of yet. Closest is Yaoi which of often depicts the guys as being bi.