Tomizawa Michie, I heard, was retiring only from game roles (I believe?).  
This OVA featuring Sumire is actually to wrap up loose ends and explain in 
the series why Sumire herself is retiring.  Since Michie is retiring, Hiroi 
Ouji decided to let the character retire as well.  This was supposed to have 
been cleared up in the fourth installment of the Sakura Taisen games but as 
not, and this OVA is the one that ties it all together with the end for 
Sumire.  Hiroi and the others came to a mutual agreement that Sumire could 
not be re-cast with a different seiyuu and that it wouldn't be the same, and 
so they decided to retire her character.

Also, the first Sakura Taisen game is being remade for the year 2003/4?  
Can't remember which one.  Anyway, there will be a new episode, but nothing 
will be changed too much.  The battle system will be upgraded to match the 
ARMS battle system that's in Sakura Taisen 3 and Sakura Taisen 4.  Much 
confusion on this too, btu Tomizawa Michie will be there to record new lines 
for Sakura Taisen 1.  Yes, she's still retired, but since it's just a remake, 
she agreed to do some lines in it.

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mink -- mink@broken-echo.net
www.broken-echo.net/mink/ - slowly coming up